feat: add 121. Best time to buy and sell stock

Author: nphausg

.gitignore

@@ -22,3 +22,4 @@
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
 src/.DS_Store
+src/com/nphausg/.DS_Store

README.md

@@ -16,23 +16,31 @@
 LeetCode is the best platform to help you enhance your skills, expand your knowledge and prepare for technical
 interviews.
 
-https://leetcode.com/nphausg
-
-🔥 Easy 🔥🔥 Medium 🔥🔥🔥 Hard
-
-## 💎 Coding Challenge
-
-| Challenge                                                                                                        | Level  | Java                                                                      | Kotlin                                                            |
-|------------------------------------------------------------------------------------------------------------------|--------|---------------------------------------------------------------------------|-------------------------------------------------------------------|
-| [20. ValidParentheses](https://leetcode.com/problems/valid-parentheses)                                          | 🔥     | [Solution](src/com/nphausg/leetcode/easy/ValidParentheses.java)           | -                                                                 |
-| [26. Remove Duplicates](https://leetcode.com/problems/remove-duplicates-from-sorted-array)                       | 🔥     | [Solution](src/com/nphausg/leetcode/easy/RemoveDuplicates.java)           | -                                                                 |
-| [27. Remove Element](https://leetcode.com/problems/remove-element)                                               | 🔥     | [Solution](src/com/nphausg/leetcode/easy/RemoveElement.java)              | -                                                                 |
-| [1929. Concatenation Of Array](https://leetcode.com/problems/concatenation-of-array)                             | 🔥     | [Solution](src/com/nphausg/leetcode/easy/ConcatenationArray.java)         | -                                                                 |
-| [17. Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number) | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/LetterCombinations.java)       | -                                                                 |
-| [91. Decode Ways ](https://leetcode.com/problems/decode-ways)                                                    | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/DecodeWays.java)               | -                                                                 |
-| [1143. Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence)                     | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/LongestCommonSubsequence.java) |
-| [658. Find K Closest Elements](https://leetcode.com/problems/find-k-closest-elements)                            | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/FindClosestElements.java)      | -                                                                 |
-| [41. First Missing Positive](https://leetcode.com/problems/first-missing-positive)                               | 🔥🔥🔥 | [Solution](src/com/nphausg/leetcode/hard/FirstMissingPositive.java)       | [Solution](src/com/nphausg/leetcode/hard/FirstMissingPositive.kt) |
+Leetcode: https://leetcode.com/nphausg
+
+Medium: https://medium.com/@nphausg
+
+🔥 Easy
+
+🔥🔥 Medium
+
+🔥🔥🔥 Hard
+
+## 💎 Coding Challenges
+
+| Challenge                                                                                                          | Level  | Java                                                                        | Kotlin                                                            |
+|--------------------------------------------------------------------------------------------------------------------|--------|-----------------------------------------------------------------------------|-------------------------------------------------------------------|
+| [0001. Two sum](https://leetcode.com/problems/two-sum)                                                             | 🔥     | -                                                                           | [Solution](src/com/nphausg/leetcode/easy/TwoSum.kt)      |
+| [0020. ValidParentheses](https://leetcode.com/problems/valid-parentheses)                                          | 🔥     | [Solution](src/com/nphausg/leetcode/easy/ValidParentheses.java)             | -                                                                 |
+| [0026. Remove Duplicates](https://leetcode.com/problems/remove-duplicates-from-sorted-array)                       | 🔥     | [Solution](src/com/nphausg/leetcode/easy/RemoveDuplicates.java)             | -                                                                 |
+| [0027. Remove Element](https://leetcode.com/problems/remove-element)                                               | 🔥     | [Solution](src/com/nphausg/leetcode/easy/RemoveElement.java)                | -                                                                 |
+| [0121. Best time to buy and sell stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock)             | 🔥     | -                                                                           | [Solution](src/com/nphausg/leetcode/easy/BuyAndSellStock.kt)      |
+| [1929. Concatenation Of Array](https://leetcode.com/problems/concatenation-of-array)                               | 🔥     | [Solution](src/com/nphausg/leetcode/easy/ConcatenationArray.java)           | -                                                                 |
+| [0017. Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number) | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/LetterCombinations.java)         | -                                                                 |
+| [0091. Decode Ways ](https://leetcode.com/problems/decode-ways)                                                    | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/DecodeWays.java)                 | -                                                                 |
+| [1143. Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence)                       | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/LongestCommonSubsequence.java)   |
+| [0658. Find K Closest Elements](https://leetcode.com/problems/find-k-closest-elements)                             | 🔥🔥   | [Solution](src/com/nphausg/leetcode/medium/FindClosestElements.java)        | -                                                                 |
+| [0041. First Missing Positive](https://leetcode.com/problems/first-missing-positive)                               | 🔥🔥🔥 | [Solution](src/com/nphausg/leetcode/hard/FirstMissingPositive.java)         | [Solution](src/com/nphausg/leetcode/hard/FirstMissingPositive.kt) |
 
 ![-----------------------------------------------------](https://raw.githubusercontent.com/andreasbm/readme/master/assets/lines/colored.png)
 

src/com/nphausg/leetcode/.DS_Store

@@ -5,7 +5,7 @@
  */
 package com.nphausg.leetcode;
 
-import com.nphausg.leetcode.medium.LongestCommonSubsequence;
+import com.nphausg.leetcode.practice.Practice;
 
 public class Main {
 
@@ -23,6 +23,7 @@ public static void main(String[] args) {
         // String text1 = "abc";
         // String text2 = "def";
 
-        System.out.println(LongestCommonSubsequence.longestCommonSubsequence(text1, text2));
+        // System.out.println(LongestCommonSubsequence.longestCommonSubsequence(text1, text2));
+        System.out.println(Practice.powerOf2(50));
     }
 }

src/com/nphausg/leetcode/Main.java

@@ -0,0 +1,24 @@
+package com.nphausg.leetcode.easy
+
+/**
+ * <a href="https://leetcode.com/problems/best-time-to-buy-and-sell-stock">Buy and Sell stock </a>
+ * */
+object BuyAndSellStock {
+
+    fun maxProfit(prices: IntArray): Int {
+        var maxProfit = 0
+        var minPrice = Int.MAX_VALUE
+
+        for (price in prices) {
+            if (price < minPrice) {
+                minPrice = price // Update the minimum price
+            } else {
+                val profit = price - minPrice // Calculate potential profit
+                if (profit > maxProfit) {
+                    maxProfit = profit // Update max profit if needed
+                }
+            }
+        }
+        return maxProfit
+    }
+}

src/com/nphausg/leetcode/easy/BuyAndSellStock.kt

@@ -6,7 +6,7 @@
 package com.nphausg.leetcode.easy;
 
 /**
- * <a href="https://leetcode.com/problems/remove-element/">...</a>
+ * <a href="https://leetcode.com/problems/remove-element/">Remove Element</a>
  */
 public class RemoveElement {
 

src/com/nphausg/leetcode/easy/RemoveElement.java

@@ -0,0 +1,30 @@
+package com.nphausg.leetcode.easy
+
+/**
+ * <a href="https://leetcode.com/problems/two-sum">Two Sum</a>
+ * */
+object TwoSum {
+
+    fun solution_brute_force(nums: IntArray, target: Int): IntArray {
+        for (i in nums.indices) {
+            for (j in i + 1 until nums.size) {
+                if (nums[i] + nums[j] == target) {
+                    return intArrayOf(i, j)
+                }
+            }
+        }
+        throw IllegalArgumentException("No two sum solution")
+    }
+
+    fun solution_hash_map(nums: IntArray, target: Int): IntArray {
+        val map = mutableMapOf<Int, Int>()
+        for (i in nums.indices) {
+            val complement = target - nums[i]
+            if (map.containsKey(complement)) {
+                return intArrayOf(map[complement]!!, i)
+            }
+            map[nums[i]] = i
+        }
+        throw IllegalArgumentException("No two sum solution")
+    }
+}

src/com/nphausg/leetcode/easy/TwoSum.kt

@@ -0,0 +1,22 @@
+package com.nphausg.leetcode.practice;
+
+/**
+ * The following function prints the powers of 2 from 1 through n (inclusive).
+ * For example, if n is 4, it would be print 1, 2, and 4.
+ */
+public class Practice {
+
+    public static int powerOf2(int n) {
+        if (n < 1) {
+            return 0;
+        }
+        if (n == 1) {
+            System.out.println(1);
+            return 1;
+        }
+        int prev = powerOf2(n / 2);
+        int curr = prev * 2;
+        System.out.println(curr);
+        return curr;
+    }
+}