Set Matrix Zeroes leetcode

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

click to show follow up.

 

Subscribe to see which companies asked this question

方法：用矩阵中的某一零行来记录零列的信息

过程如下：

1.从下往上遍历矩阵，找到第一个0元素，我们将其所在行作为记录行，用它来记录列号

2.接着从上向下遍历矩阵，找到0元素，将其所在行赋值为0，并在记录行中同列的元素赋值为0，作为记录

3.根据记录行中的记录，将0元素所在的列全部赋值为0

4.将记录行赋值为0

void setZeroes(vector<vector<int>>& matrix) {
    const int h = matrix.size();
    const int w = matrix[0].size();
    int store = -1;
    for (int i = h - 1; i >= 0; --i)
    {
        if (store != -1)
            break;
        for (int j = 0; j < w; ++j)
        {
            if (matrix[i][j] == 0)
            {
                store = i;
                break;
            }
        }
    }
    if (store == -1)
        return;
    for (int i = 0; i < store; ++i)
    {
        bool isZero = false;
        for (int j = 0; j < w; ++j)
        {
            if (matrix[i][j] == 0)
            {
                matrix[store][j] = 0;
                isZero = true;
            }
        }
        if (isZero)
            for (int j = 0; j < w; ++j)
                matrix[i][j] = 0;
    }

    for (int j = 0; j < w; ++j)
        if(matrix[store][j] == 0)
            for (int i = 0; i < h; ++i)
                matrix[i][j] = 0;

    for (int j = 0; j < w; ++j)
        matrix[store][j] = 0;
}