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Author: BaffinLee

101-200/169. Majority Element.md

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+# 169. Majority Element
+
+- Difficulty: Easy.
+- Related Topics: Array, Divide and Conquer, Bit Manipulation.
+- Similar Questions: Majority Element II.
+
+## Problem
+
+Given an array of size *n*, find the majority element. The majority element is the element that appears **more than** ```⌊ n/2 ⌋``` times.
+
+You may assume that the array is non-empty and the majority element always exist in the array.
+
+**Example 1:**
+
+```
+Input: [3,2,3]
+Output: 3
+```
+
+**Example 2:**
+
+```
+Input: [2,2,1,1,1,2,2]
+Output: 2
+```
+
+## Solution 1
+
+```javascript
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var majorityElement = function(nums) {
+  var map = {};
+  var max = 0;
+  var majorNum = 0;
+  var len = nums.length;
+  for (var i = 0; i < len; i++) {
+    if (!map[nums[i]]) map[nums[i]] = 0;
+    map[nums[i]]++;
+    if (map[nums[i]] > max) {
+      majorNum = nums[i];
+      max = map[nums[i]];
+    }
+  }
+  return majorNum;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).
+
+## Solution 2
+
+```javascript
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var majorityElement = function(nums) {
+  var count = 0;
+  var majorNum = 0;
+  var len = nums.length;
+  for (var i = 0; i < len; i++) {
+    if (!count) {
+      majorNum = nums[i];
+      count = 1;
+    } else {
+      count += (nums[i] === majorNum ? 1 : -1);
+    }
+  }
+  return majorNum;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).