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‎Problemset/1106-Parsing A Boolean Expression/README.md

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# 1106. Parsing A Boolean Expression
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A **boolean expression** is an expression that evaluates to either `true` or `false`. It can be in one of the following shapes:
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* `'t'` that evaluates to `true`.
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* `'f'` that evaluates to `false`.
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* `'!(subExpr)'` that evaluates to **the logical NOT** of the inner expression `subExpr`.
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* `'&(subExpr1, subExpr2, ..., subExprn)'` that evaluates to **the logical AND** of the inner expressions `subExpr1, subExpr2, ..., subExprn` where `n >= 1`.
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* `'|(subExpr1, subExpr2, ..., subExprn)'` that evaluates to **the logical OR** of the inner expressions `subExpr1, subExpr2, ..., subExprn` where `n >= 1`.
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Given a string `expression` that represents a **boolean expression**, return *the evaluation of that expression*.
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It is **guaranteed** that the given expression is valid and follows the given rules.
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#### Example 1:
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<pre>
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<strong>Input:</strong> expression = "&(|(f))"
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<strong>Output:</strong> false
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<strong>Explanation:</strong>
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First, evaluate |(f) --> f. The expression is now "&(f)".
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Then, evaluate &(f) --> f. The expression is now "f".
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Finally, return false.
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</pre>
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#### Example 2:
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<pre>
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<strong>Input:</strong> expression = "|(f,f,f,t)"
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<strong>Output:</strong> true
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<strong>Explanation:</strong> The evaluation of (false OR false OR false OR true) is true.
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</pre>
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#### Example 3:
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<pre>
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<strong>Input:</strong> expression = "!(&(f,t))"
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<strong>Output:</strong> true
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<strong>Explanation:</strong>
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First, evaluate &(f,t) --> (false AND true) --> false --> f. The expression is now "!(f)".
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Then, evaluate !(f) --> NOT false --> true. We return true.
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</pre>
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#### Constraints:
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* <code>1 <= expression.length <= 2 * 10<sup>4</sup></code>
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* expression[i] is one following characters: `'('`, `')'`, `'&'`, `'|'`, `'!'`, `'t'`, `'f'`, and `','`.
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## Solutions (Rust)
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### 1. Solution
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```Rust
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impl Solution {
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pub fn parse_bool_expr(expression: String) -> bool {
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let mut ops = vec![];
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let mut bools = vec![];
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for ch in expression.chars() {
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match ch {
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'!' | '&' | '|' => ops.push(ch),
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't' | 'f' => bools.push(Some(ch == 't')),
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')' => match ops.pop() {
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Some('!') => {
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let tmp = !bools.pop().unwrap().unwrap();
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bools.pop();
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bools.push(Some(tmp));
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}
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Some('&') => {
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let mut tmp = true;
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while let Some(Some(b)) = bools.pop() {
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tmp &= b;
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}
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bools.push(Some(tmp));
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}
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Some('|') => {
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let mut tmp = false;
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while let Some(Some(b)) = bools.pop() {
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tmp |= b;
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}
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bools.push(Some(tmp));
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}
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_ => {
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let tmp = bools.pop().unwrap();
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bools.pop();
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bools.push(tmp);
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}
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},
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'(' => bools.push(None),
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_ => (),
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}
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}
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bools[0].unwrap()
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}
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}
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```

‎Problemset/1106-Parsing A Boolean Expression/README_CN.md

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# 1106. 解析布尔表达式
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**布尔表达式** 是计算结果不是 `true` 就是 `false` 的表达式。有效的表达式需遵循以下约定：
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* `'t'`，运算结果为 `true`
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* `'f'`，运算结果为 `false`
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* `'!(subExpr)'`，运算过程为对内部表达式 `subExpr` 进行 **逻辑非**（NOT）运算
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* `'&(subExpr1, subExpr2, ..., subExprn)'`，运算过程为对 2 个或以上内部表达式 `subExpr1, subExpr2, ..., subExprn` 进行 **逻辑与**（AND）运算
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* `'|(subExpr1, subExpr2, ..., subExprn)'`，运算过程为对 2 个或以上内部表达式 `subExpr1, subExpr2, ..., subExprn` 进行 **逻辑或**（OR）运算
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给你一个以字符串形式表述的 [布尔表达式](https://baike.baidu.com/item/%E5%B8%83%E5%B0%94%E8%A1%A8%E8%BE%BE%E5%BC%8F/1574380?fr=aladdin) `expression`，返回该式的运算结果。
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题目测试用例所给出的表达式均为有效的布尔表达式，遵循上述约定。
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#### 示例 1:
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<pre>
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<strong>输入:</strong> expression = "&(|(f))"
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<strong>输出:</strong> false
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<strong>解释:</strong>
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首先，计算 |(f) --> f ，表达式变为 "&(f)" 。
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接着，计算 &(f) --> f ，表达式变为 "f" 。
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最后，返回 false 。
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</pre>
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#### 示例 2:
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<pre>
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<strong>输入:</strong> expression = "|(f,f,f,t)"
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<strong>输出:</strong> true
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<strong>解释:</strong> 计算 (false OR false OR false OR true) ，结果为 true 。
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</pre>
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#### 示例 3:
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<pre>
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<strong>输入:</strong> expression = "!(&(f,t))"
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<strong>输出:</strong> true
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<strong>解释:</strong>
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首先，计算 &(f,t) --> (false AND true) --> false --> f ，表达式变为 "!(f)" 。
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接着，计算 !(f) --> NOT false --> true ，返回 true 。
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</pre>
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#### 提示:
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* <code>1 <= expression.length <= 2 * 10<sup>4</sup></code>
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* `expression[i]` 为 `'('`、`')'`、`'&'`、`'|'`、`'!'`、`'t'`、`'f'` 和 `','` 之一
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## 题解 (Rust)
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### 1. 题解
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```Rust
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impl Solution {
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pub fn parse_bool_expr(expression: String) -> bool {
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let mut ops = vec![];
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let mut bools = vec![];
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for ch in expression.chars() {
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match ch {
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'!' | '&' | '|' => ops.push(ch),
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't' | 'f' => bools.push(Some(ch == 't')),
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')' => match ops.pop() {
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Some('!') => {
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let tmp = !bools.pop().unwrap().unwrap();
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bools.pop();
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bools.push(Some(tmp));
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}
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Some('&') => {
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let mut tmp = true;
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while let Some(Some(b)) = bools.pop() {
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tmp &= b;
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}
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bools.push(Some(tmp));
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}
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Some('|') => {
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let mut tmp = false;
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while let Some(Some(b)) = bools.pop() {
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tmp |= b;
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}
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bools.push(Some(tmp));
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}
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_ => {
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let tmp = bools.pop().unwrap();
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bools.pop();
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bools.push(tmp);
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}
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},
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'(' => bools.push(None),
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_ => (),
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}
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}
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bools[0].unwrap()
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}
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}
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```

‎Problemset/1106-Parsing A Boolean Expression/Solution.rs

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impl Solution {
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pub fn parse_bool_expr(expression: String) -> bool {
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let mut ops = vec![];
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let mut bools = vec![];
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for ch in expression.chars() {
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match ch {
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'!' | '&' | '|' => ops.push(ch),
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't' | 'f' => bools.push(Some(ch == 't')),
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')' => match ops.pop() {
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Some('!') => {
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let tmp = !bools.pop().unwrap().unwrap();
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bools.pop();
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bools.push(Some(tmp));
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}
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Some('&') => {
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let mut tmp = true;
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while let Some(Some(b)) = bools.pop() {
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tmp &= b;
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}
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bools.push(Some(tmp));
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}
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Some('|') => {
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let mut tmp = false;
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while let Some(Some(b)) = bools.pop() {
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tmp |= b;
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}
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bools.push(Some(tmp));
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}
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_ => {
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let tmp = bools.pop().unwrap();
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bools.pop();
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bools.push(tmp);
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}
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},
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'(' => bools.push(None),
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_ => (),
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}
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}
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bools[0].unwrap()
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}
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}

‎README.md

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[1094][1094l]|[Car Pooling][1094] |![rs]
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[1103][1103l]|[Distribute Candies to People][1103] |![py]
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[1104][1104l]|[Path In Zigzag Labelled Binary Tree][1104] |![rs]
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[1106][1106l]|[Parsing A Boolean Expression][1106] |![rs]
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[1108][1108l]|[Defanging an IP Address][1108] |![rs]
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[1109][1109l]|[Corporate Flight Bookings][1109] |![rs]
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[1110][1110l]|[Delete Nodes And Return Forest][1110] |![py]&nbsp;&nbsp;![rb]
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[1094]:Problemset/1094-Car%20Pooling/README.md#1094-car-pooling
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[1103]:Problemset/1103-Distribute%20Candies%20to%20People/README.md#1103-distribute-candies-to-people
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[1104]:Problemset/1104-Path%20In%20Zigzag%20Labelled%20Binary%20Tree/README.md#1104-path-in-zigzag-labelled-binary-tree
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[1106]:Problemset/1106-Parsing%20A%20Boolean%20Expression/README.md#1106-parsing-a-boolean-expression
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[1108]:Problemset/1108-Defanging%20an%20IP%20Address/README.md#1108-defanging-an-ip-address
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[1109]:Problemset/1109-Corporate%20Flight%20Bookings/README.md#1109-corporate-flight-bookings
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[1110]:Problemset/1110-Delete%20Nodes%20And%20Return%20Forest/README.md#1110-delete-nodes-and-return-forest
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[1094l]:https://leetcode.com/problems/car-pooling/
34683470
[1103l]:https://leetcode.com/problems/distribute-candies-to-people/
34693471
[1104l]:https://leetcode.com/problems/path-in-zigzag-labelled-binary-tree/
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[1106l]:https://leetcode.com/problems/parsing-a-boolean-expression/
34703473
[1108l]:https://leetcode.com/problems/defanging-an-ip-address/
34713474
[1109l]:https://leetcode.com/problems/corporate-flight-bookings/
34723475
[1110l]:https://leetcode.com/problems/delete-nodes-and-return-forest/

‎README_CN.md

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[1094][1094l]|[拼车][1094] |![rs]
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[1103][1103l]|[分糖果 II][1103] |![py]
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[1104][1104l]|[二叉树寻路][1104] |![rs]
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[1106][1106l]|[解析布尔表达式][1106] |![rs]
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[1108][1108l]|[IP 地址无效化][1108] |![rs]
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[1109][1109l]|[航班预订统计][1109] |![rs]
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[1110][1110l]|[删点成林][1110] |![py]&nbsp;&nbsp;![rb]
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[1094]:Problemset/1094-Car%20Pooling/README_CN.md#1094-拼车
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[1103]:Problemset/1103-Distribute%20Candies%20to%20People/README_CN.md#1103-分糖果-ii
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[1104]:Problemset/1104-Path%20In%20Zigzag%20Labelled%20Binary%20Tree/README_CN.md#1104-二叉树寻路
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[1106]:Problemset/1106-Parsing%20A%20Boolean%20Expression/README_CN.md#1106-解析布尔表达式
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[1108]:Problemset/1108-Defanging%20an%20IP%20Address/README_CN.md#1108-ip-地址无效化
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[1109]:Problemset/1109-Corporate%20Flight%20Bookings/README_CN.md#1109-航班预订统计
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[1110]:Problemset/1110-Delete%20Nodes%20And%20Return%20Forest/README_CN.md#1110-删点成林
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[1094l]:https://leetcode.cn/problems/car-pooling/
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[1103l]:https://leetcode.cn/problems/distribute-candies-to-people/
34693471
[1104l]:https://leetcode.cn/problems/path-in-zigzag-labelled-binary-tree/
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[1106l]:https://leetcode.cn/problems/parsing-a-boolean-expression/
34703473
[1108l]:https://leetcode.cn/problems/defanging-an-ip-address/
34713474
[1109l]:https://leetcode.cn/problems/corporate-flight-bookings/
34723475
[1110l]:https://leetcode.cn/problems/delete-nodes-and-return-forest/

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