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class Solution {//let the first row and first col to keep the record//if matrix[row][col] == 0 && col == 0, then firstColZero = true, same to firstRowZeropublic:	void setZeroes(vector
   
    
      > &matrix) {		// Start typing your C/C++ solution below		// DO NOT write int main() function		int rowNum = matrix.size();		if(0 == rowNum) return;		int colNum = matrix[0].size();		bool firstRowZero, firstColumnZero;		firstRowZero = firstColumnZero = false;		for (int row = 0; row < rowNum; ++row)		{			for (int col = 0; col < colNum; ++col)			{				if (!matrix[row][col])				{					if(row == 0) firstRowZero = true;					if(col == 0) firstColumnZero = true;					matrix[row][0] = 0;					matrix[0][col] = 0;				}			}		}		//according the flag in first row and first col to set the row and col to zero corresponding		for(int row = 1; row < rowNum; ++row)		{			if(0 == matrix[row][0])			{				for (int col = 0; col < colNum; ++col)					matrix[row][col] = 0;			}		}		//		for(int col = 1; col < colNum; ++col)		{			if(0 == matrix[0][col])			{				for (int row = 0; row < rowNum; ++row)					matrix[row][col] = 0;			}		}		//		if(firstRowZero)			for (int col = 0; col < colNum; ++col)				matrix[0][col] = 0;		if(firstColumnZero)			for (int row = 0; row < rowNum; ++row)				matrix[row][0] = 0;	}};
    
   

second time

class Solution {public:    void setZeroes(vector
   
    
      > &matrix) {		// Start typing your C/C++ solution below		// DO NOT write int main() function		int n = matrix.size();		if(n == 0) return;		int m = matrix[0].size();		if(m == 0) return;		bool firstRow = false;		bool firstColumn = false;		for(int i = 0; i < n; ++i) 		{			if(matrix[i][0] == 0)			{				firstColumn = true;				break;			}		}		for(int j = 0; j < m; ++j) 		{			if(matrix[0][j] == 0)			{				firstRow = true;				break;			}		}		//using first row and first column to keep record		for(int i = 1; i < n; ++i)		{			for(int j = 1; j < m; ++j)			{				if(matrix[i][j] == 0) matrix[0][j] = 0, matrix[i][0] = 0;			}		}		//set zero		for(int i = 1; i < n; ++i)		{			if(matrix[i][0] == 0) 			{				for(int j = 1; j < m; ++j) matrix[i][j] = 0;			}		}		for(int j = 1; j < m; ++j)		{			if(matrix[0][j] == 0)			{				for(int i = 1; i < n; ++i) matrix[i][j] = 0;			}		}		//set first row and first colum		if(firstRow) 		{			for(int j = 0; j < m; ++j) matrix[0][j] = 0;		}		if(firstColumn)		{			for(int i = 0; i < n; ++i) matrix[i][0] = 0;		}	}};
    
   

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