【摩尔投票法】求数组中出现次数超过一半的数

摩尔投票法

学习资料：
1.算法讲解116【扩展】摩尔投票大加强，线段树里捉海王

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练习题

169.多数元素

写法一

class Solution {
public:
    //摩尔投票法 https://www.bilibili.com/video/BV1Br421G7hB/
    int majorityElement(vector<int>& nums) {
        int val = 0, cnt = 0;
        for (int &x : nums)
        {
            if (cnt == 0) val = x, cnt = 1; //下面两行是每个写法的区别
            else if (val == x) cnt++;
            else cnt--;
        }
        cnt = 0;
        for (int &x : nums) 
            if (x == val)
                cnt++;
        if (cnt > nums.size() / 2) return val;
        return -1;
    }
};

写法二

class Solution {
public:
    //摩尔投票法 https://www.bilibili.com/video/BV1Br421G7hB/
    int majorityElement(vector<int>& nums) {
        int val = 0, cnt = 0;
        for (int &x : nums)
        {
            if (cnt == 0) val = x, cnt = 1;//下面两行是每个写法的区别
            else if (val != x) cnt--;
            else cnt++;
        }
        cnt = 0;
        for (int &x : nums) 
            if (x == val)
                cnt++;
        if (cnt > nums.size() / 2) return val;
        return -1;
    }
};

写法三

class Solution {
public:
    int majorityElement(vector<int>& nums) {
        int val = 0, cnt = 0;
        for (int &x : nums)
        {
            if (cnt == 0) val = x, cnt = 1;//下面两行是每个写法的区别
            else if (val != x) cnt--;
            else if (val == x) cnt++;
        }
        cnt = 0;
        for (int &x : nums) 
            if (x == val)
                cnt++;
        if (cnt > nums.size() / 2) return val;
        return -1;
    }
};