73. Set Matrix Zeroes

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

第一行和第一列记录每一列和每一行是否出现过0。另外用两个变量记录第一行和第一列是否出现过0.

class Solution {
public:
void setZeroes(vector<vector<int> >& matrix) {
bool rowZero = false, colZero = false;
for (int i = 0; i < matrix[0].size(); i++){
if (matrix[0][i] == 0){
rowZero = true;
break;
}
}
for (int i = 0; i < matrix.size(); i++){
if (matrix[i][0] == 0){
colZero = true;
break;
}
}

for (int i = 1; i < matrix.size(); i++){
for (int j = 1; j < matrix[0].size(); j++){
if (matrix[i][j] == 0){
matrix[i][0] = matrix[0][j] = 0;
}
}
}

for (int i = 1; i < matrix.size(); i++){
for (int j = 1; j < matrix[0].size(); j++){
if (matrix[i][0]==0||matrix[0][j]==0){
matrix[i][j] = 0;
}
}
}

if (rowZero){
for (int i = 0; i < matrix[0].size(); i++){
matrix[0][i] = 0;
}
}
if (colZero){
for (int i = 0; i < matrix.size(); i++){
matrix[i][0] = 0;
}
}

}
};