73. 矩陣置零

自己做

解：標記消除

class Solution {
public:void setZeroes(vector<vector<int>>& matrix) {vector<bool> x(matrix.size(), false);              //要置0的行vector<bool> y(matrix[0].size(), false);           //要置0的列//找出所有0元素for(int i = 0; i < (int)matrix.size(); i++)for(int j = 0; j < (int)matrix[0].size(); j++)if(matrix[i][j] == 0){x[i] = true;        //該行要置0y[j] = true;        //該列要置0}//置空行   for(int i = 0; i < (int)matrix.size(); i++)if(x[i])                   //該行需要置0for(int j = 0; j < (int)matrix[0].size(); j++)matrix[i][j] = 0;//置空列for(int j = 0; j < (int)matrix[0].size(); j++)        if(y[j])                   //該列需要置0for(int i = 0; i < (int)matrix.size(); i++)matrix[i][j] = 0;}
};

看題解

解：利用已有空間保存數據

官方代碼：

class Solution {
public:void setZeroes(vector<vector<int>>& matrix) {int m = matrix.size();int n = matrix[0].size();int flag_col0 = false, flag_row0 = false;for (int i = 0; i < m; i++) {if (!matrix[i][0]) {flag_col0 = true;}}for (int j = 0; j < n; j++) {if (!matrix[0][j]) {flag_row0 = true;}}for (int i = 1; i < m; i++) {for (int j = 1; j < n; j++) {if (!matrix[i][j]) {matrix[i][0] = matrix[0][j] = 0;}}}for (int i = 1; i < m; i++) {for (int j = 1; j < n; j++) {if (!matrix[i][0] || !matrix[0][j]) {matrix[i][j] = 0;}}}if (flag_col0) {for (int i = 0; i < m; i++) {matrix[i][0] = 0;}}if (flag_row0) {for (int j = 0; j < n; j++) {matrix[0][j] = 0;}}}
};