169. 多数元素

Author: w2xi

README.md

@@ -79,6 +79,7 @@
 |151|[颠倒字符串中的单词](https://leetcode.cn/problems/reverse-words-in-a-string/)|[JavaScript](./algorithms/reverse-words-in-a-string.js)|Medium|
 |155|[最小栈](https://leetcode.cn/problems/min-stack/)|[JavaScript](./algorithms/min-stack.js)|Easy|
 |160|[相交链表](https://leetcode.cn/problems/intersection-of-two-linked-lists/)|[JavaScript](./algorithms/intersection-of-two-linked-lists.js)|Easy|
+|169|[多数元素](https://leetcode.cn/problems/majority-element/)|[JavaScript](./algorithms/majority-element.js)|Easy|
 |173|[二叉搜索树迭代器](https://leetcode.cn/problems/binary-search-tree-iterator/)|[JavaScript](./algorithms/binary-search-tree-iterator.js)|Medium|
 |189|[轮转数组](https://leetcode-cn.com/problems/rotate-array/)|[JavaScript](./algorithms/rotate-array.js)|Medium|
 |199|[二叉树的右视图](https://leetcode.cn/problems/binary-tree-right-side-view/)|[JavaScript](./algorithms/binary-tree-right-side-view.js)|Medium|

algorithms/majority-element.js

@@ -0,0 +1,21 @@
+/**
+ * 169. 多数元素
+ * @param {number[]} nums
+ * @return {number}
+ */
+var majorityElement = function (nums) {
+  // 哈希表
+  // 时间复杂度: O(n)
+  // 空间复杂度: O(n)
+
+  const targetNum = nums.length >> 1;
+  const map = {};
+
+  for (let i = 0; i < nums.length; i++) {
+    let curr = nums[i];
+    map[curr] = (map[curr] || 0) + 1;
+    if (map[curr] > targetNum) {
+      return curr;
+    }
+  }
+};