【LeetCode 0169】【摩尔投票算法】主元素

169. Majority Element

Given an array nums of size n, return the majority element.

The majority element is the element that appears more than ⌊n / 2⌋ times. You may assume that the majority element always exists in the array.

Example 1:

**Input:** nums = [3,2,3]
**Output:** 3

Example 2:

**Input:** nums = [2,2,1,1,1,2,2]
**Output:** 2

Constraints:

• n == nums.length
• 1 <= n <= 5 * 10^4
• -10^9 <= nums[i] <= 10^9

Follow-up: Could you solve the problem in linear time and in O(1) space?

Idea

Boyer Moore Vote Algorithm 

JavaScript Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var majorityElement = function(nums) {
    [res,count] = [nums[0],0]
    for(let n of nums){
        if(count == 0){
            [res,count] = [n,1]
        }else{
            if(res == n){
                count ++
            }else{
                count --
            }
        }
    }
    return res;
};
```