feat: add 137. Single Number II

Author: nphausg

README.md

@@ -10,6 +10,15 @@
  * <a href="https://leetcode.com/problems/single-number">136. Single Number</a>
  */
 public class SingleNumber {
+
+    public static int singleNumber2(int[] nums) {
+        int result = 0;
+        for (int num : nums) {
+            result ^= num;
+        }
+        return result;
+    }
+
     public static int singleNumber(int[] nums) {
         HashMap<Integer, Integer> map = new HashMap<>();
         for (int num : nums) {
@@ -27,9 +36,10 @@ public static class TestCase extends BaseTest {
 
         @org.junit.Test
         public void testCases() {
-            assertEquals(1, singleNumber(new int[]{1}));
-            assertEquals(1, singleNumber(new int[]{2, 2, 1}));
-            assertEquals(4, singleNumber(new int[]{4, 1, 2, 1, 2}));
+            assertEquals(1, singleNumber2(new int[]{1}));
+            assertEquals(1, singleNumber2(new int[]{2, 2, 1}));
+            assertEquals(4, singleNumber2(new int[]{4, 1, 2, 1, 2}));
         }
     }
 }
+

docs/images/buymeacoffee.webp

@@ -0,0 +1,43 @@
+package com.nphausg.leetcode.medium;
+
+import com.nphausg.leetcode.config.BaseTest;
+
+import java.util.HashMap;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * <a href="https://leetcode.com/problems/single-number-ii">137. Single Number II</a>
+ */
+public class SingleNumberII {
+
+    public static int singleNumber2(int[] nums) {
+        int ones = 0, twos = 0;
+        for (int num : nums) {
+            ones = (ones ^ num) & ~twos;
+            twos = (twos ^ num) & ~ones;
+        }
+        return ones;
+    }
+    public static int singleNumber(int[] nums) {
+        HashMap<Integer, Integer> map = new HashMap<>();
+        for (int num : nums) {
+            map.put(num, map.getOrDefault(num, 0) + 1);
+        }
+        for (int num : map.keySet()) {
+            if (map.get(num) == 1) {
+                return num;
+            }
+        }
+        return -1;
+    }
+
+    public static class TestCase extends BaseTest {
+
+        @org.junit.Test
+        public void testCases() {
+            assertEquals(3, singleNumber2(new int[]{2, 2, 3, 2}));
+            assertEquals(99, singleNumber2(new int[]{0, 1, 0, 1, 0, 1, 99}));
+        }
+    }
+}

docs/images/leetcode.png

@@ -0,0 +1,54 @@
+package com.nphausg.leetcode.medium;
+
+
+import com.nphausg.leetcode.config.BaseTest;
+
+import java.util.HashMap;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * <a href="https://leetcode.com/problems/single-number-iii">260. Single Number III</a>
+ */
+public class SingleNumberIII {
+
+    public static int[] singleNumber2(int[] nums) {
+        int xor = 0;
+        for (int num : nums) {
+            xor ^= num; // XOR toàn bộ mảng
+        }
+        int diff = xor & (-xor); // Lấy bit khác biệt
+        int[] result = new int[2];
+        for (int num : nums) {
+            if ((num & diff) == 0) {
+                result[0] ^= num;
+            } else {
+                result[1] ^= num;
+            }
+        }
+        return result;
+    }
+
+    public static int singleNumber(int[] nums) {
+        HashMap<Integer, Integer> map = new HashMap<>();
+        for (int num : nums) {
+            map.put(num, map.getOrDefault(num, 0) + 1);
+        }
+        for (int num : map.keySet()) {
+            if (map.get(num) == 1) {
+                return num;
+            }
+        }
+        return -1;
+    }
+
+    public static class TestCase extends BaseTest {
+
+        @org.junit.Test
+        public void testCases() {
+            assertEquals(1, singleNumber2(new int[]{1}));
+            assertEquals(1, singleNumber2(new int[]{2, 2, 1}));
+            assertEquals(4, singleNumber2(new int[]{4, 1, 2, 1, 2}));
+        }
+    }
+}