169. Majority Element LeetCode

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.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

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class Solution {public:    int majorityElement(vector<int>& nums) {        stack<int> st;        int n=nums.size();        st.push(nums[0]);//将nums的第一个元素放入栈中        for(int i=1;i<n;i++)        {            if(nums[i]!=st.top()) //不同则退栈，栈空则压入下一个nums中的元素            {                st.pop();                if(st.empty())                {                    i++;                    st.push(nums[i]);                }            }            else st.push(nums[i]);        }        return st.top();//返回栈顶元素即可    }};

题目分析：按照题目所述，所给样例一定存在一个个数大于等于n/2的majority，这样就可以利用两两消除的办法进行判断，就是将两个不同的数字相互抵消，则最终剩下来的一定只是majority这个数了。这就可以利用栈来做，相当容易理解。