Leetcode20: Set Matrix Zeroes

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Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

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Follow up:

Did you use extra space?
A straight forward solution using O(mn) space is probably a bad idea.
A simple improvement uses O(m + n) space, but still not the best solution.

Could you devise a constant space solution?

class Solution {public:    void setZeroes(vector<vector<int>>& matrix) {        int m = matrix.size();        int n = matrix[0].size();        bool rowzero = false;        bool colzero = false;        for(int i = 0; i < m; i++)        {            if(matrix[i][0] == 0)            {                rowzero = true;                break;            }        }                for(int j = 0; j < n; j++)        {            if(matrix[0][j] == 0)            {                colzero = true;                break;            }        }                for(int i = 1; i < m; i++)        {            for(int j = 1; j < n; j++)            {                if(matrix[i][j] == 0)                {                    matrix[0][j] = 0;                    matrix[i][0] = 0;                }            }        }                for(int i = 1; i < m; i++)        {            for(int j = 1; j < n; j++)            {                if(!matrix[0][j] || !matrix[i][0])                    matrix[i][j] = 0;            }        }                if(rowzero)        {            for(int i = 0; i < m; i++)            {                matrix[i][0] = 0;            }        }                if(colzero)        {             for(int j = 0; j < n; j++)            {                matrix[0][j] = 0;            }                    }    }};

想看看用c++写出运行70多ms的代码是啥样= =

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