Leetcode:73. Set Matrix Zeroes

Description

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

思路

在原数组上面做，如果matrix[i][j] = 0, 由于第i行，第j列都要变成0，所以将matrix[i][0] = 0, matrix[0][j] = 0，这表明将该行该列所有元素置零

特殊情况：第0行和第0列是特殊情况，单独考虑

代码

class Solution {
public:
void setZeroes(vector<vector<int>>& matrix) {
int m = matrix.size();
if(m == 0) return;
int n = matrix[0].size();

int flag_m = 0, flag_n = 0;
for(int i = 0; i < m; ++i){
for(int j = 0; j < n; ++j){
if(matrix[i][j] == 0){
if(i == 0) flag_m = 1;
if(j == 0) flag_n = 1;
matrix[i][0] = 0;
matrix[0][j] = 0;
}
}
}

int i = 1, j = 1;
for(i = 1; i < m; ++i){
for(j = 1; j < n; ++j){
if(matrix[0][j] == 0 || matrix[i][0] == 0)
matrix[i][j] = 0;
}
}

for(int i = 0; i < m; ++i){
if(flag_n)
matrix[i][0] = 0;
}

for(int j = 0; j < n; ++j){
if(flag_m)
matrix[0][j] = 0;
}
}
};