Single Number

Author: w2xi

README.md

@@ -8,6 +8,7 @@
 |9|[回文数](https://leetcode-cn.com/problems/palindrome-number/)|[JavaScript](./algorithms/palindrome-number.js)|Easy|
 |14|[最长公共前缀](https://leetcode-cn.com/problems/longest-common-prefix/)|[JavaScript](./algorithms/longest-common-prefix.js)|Easy|
 |21|[合并两个有序链表](https://leetcode-cn.com/problems/merge-two-sorted-lists/)|[JavaScript](./algorithms/merge-two-sorted-lists.js)|Easy|
+|136|[只出现一次的数字](https://leetcode-cn.com/problems/single-number/)|[JavaScript](./algorithms/single-number.js)|Easy|
 |189|[轮转数组](https://leetcode-cn.com/problems/rotate-array/)|[JavaScript](./algorithms/rotate-array.js)|Medium|
 |344|[反转字符串](https://leetcode-cn.com/problems/reverse-string/)|[JavaScript](./algorithms/reverse-string.js)|Easy|
 |349|[两个数组的交集](https://leetcode-cn.com/problems/intersection-of-two-arrays/)|[JavaScript](./algorithms/intersection-of-two-arrays.js)|Easy|

algorithms/single-number.js

@@ -0,0 +1,40 @@
+// 方法一：映射
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var singleNumber = function (nums) {
+  const o = {};
+
+  for (let i = 0; i < nums.length; i++) {
+    const curr = nums[i];
+
+    // 如果已经出现过
+    if (o[curr]) {
+      delete o[curr];
+    } else {
+      o[curr] = 1;
+    }
+  }
+
+  const keys = Object.keys(o);
+
+  return keys[0];
+};
+
+// 方法二：位运算
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+ var singleNumber = function(nums) {
+  let result = 0
+
+  for (let i = 0; i < nums.length; i++) {
+      result ^= nums[i]
+  }
+
+  return result
+};