题目
Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.
分析
- 方法一自己的思路,用两个数组分别记录行、列哪个为零
- 方法二是参考的别人的代码,直接用数组的第一行和第一列记录,但是会有点麻烦,需要用一个额外的变量存储,有点不太好理解,所以自己写了一个方法一
实现
class Solution {
public:
void setZeroes(vector < vector<int>>& matrix)
{
if (matrix.empty() || matrix.size() == 0 || matrix[0].size() == 0)
return;
int rows = matrix.size(), cols = matrix[0].size();
vector<bool> tagRows(rows, false);
vector<bool> tagCols(cols, false);
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
if (matrix[i][j] == 0)
{
tagRows[i] = true;
tagCols[j] = true;
}
}
}
for (int i = rows-1; i >=0; i--)
{
for (int j = cols-1; j >=0; j--)
{
if (tagRows[i]||tagCols[j])
matrix[i][j] = 0;
}
}
}
void setZeroesRefer(vector<vector<int>>& matrix) {
//判断是否为空
if (matrix.empty() || matrix.size() == 0 || matrix[0].size() == 0)
return ;
int col0 = 1,rows = matrix.size(), cols = matrix[0].size();
for (int i = 0; i < rows; i++)
{
if (matrix[i][0] == 0)
col0 = 0;
for (int j = 1; j < cols; j++)
{
if (matrix[i][j] == 0)
{
matrix[i][0] = 0;
matrix[0][j] = 0;
}
}
}
for (int i = 0; i < matrix.size(); i++)
{
for (int j = 0; j < matrix[0].size(); j++)
cout << matrix[i][j] << " ";
cout << endl;
}
for (int i = rows-1; i >=0;i--)
{
for (int j = cols-1; j >=0; j--)
{
if (matrix[i][0] == 0 || matrix[0][j] == 0)
matrix[i][j] = 0;
}
if (col0 == 0)
matrix[i][0] = 0;
}
}
};