1.8 Zero Matrix: Write an algorithm such that if an element in an MxN matrix is 0, its entire row and column are set to 0.
解法一：two bool arrays
void zero(vector<vector<int>> &matrix){
int n = matrix.size();
int m = matrix[0].size();
bool row[n] = {};
bool col[m] = {};
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
if(matrix[i][j]==0){
row[i] = true;
col[j] = true;
}
}
}
for(int i=0;i<n;i++){
if(row[i]){
for(int j=0;j<m;j++){
matrix[i][j] = 0;
}
}
}
for(int j=0;j<m;j++){
if(col[j]){
for(int i=0;i<n;i++){
matrix[i][j] = 0;
}
}
}
}解法二：two bool variables
void zero(vector<vector<int>> &matrix){
bool row = false;
bool col = false;
int n = matrix.size();
int m = matrix[0].size();
for(int i=0;i<n;i++){
if(matrix[i][0]==0){
col = true;
break;
}
}
for(int j=0;j<m;j++){
if(matrix[0][j]==0){
row = true;
break;
}
}
for(int i=1;i<n;i++){
for(int j=1;j<m;j++){
if(matrix[i][j]==0){
matrix[i][0] = 0;
matrix[0][j] = 0;
}
}
}
for(int i=0;i<n;i++){
if(matrix[i][0]==0){
for(int j=1;j<m;j++){
matrix[i][j] = 0;
}
}
}
for(int j=0;j<m;j++){
if(matrix[0][j]==0){
for(int i=0;i<n;i++){
matrix[i][j] = 0;
}
}
}
if(row){
for(int j=0;j<m;j++){
matrix[0][j] = 0;
}
}
if(col){
for(int i=0;i<n;i++){
matrix[i][0] = 0;
}
}
}