leetcode 之 Surrounded Regions

标签：matrix   矩阵   leetcode   

Given a 2D board containing ‘X‘ and ‘O‘, capture all regions surrounded by ‘X‘.

A region is captured by flipping all ‘O‘s into ‘X‘s in that surrounded region.

For example,

X X X X
X O O X
X X O X
X O X X

After running your function, the board should be:

X X X X
X X X X
X X X X
X O X X

class Solution {
public:
    void solve_border(vector<vector<char> >& board,int i,int j,int row,int col)
    {
    	board[i][j] = 'A';
    	if(i+1 < row && board[i+1][j] == 'O')solve_border(board,i+1,j,row,col);
    	if(j > 0 && board[i][j-1] == 'O')solve_border(board,i,j-1,row,col);
    	if(i > 0 && board[i-1][j] == 'O')solve_border(board,i-1,j,row,col);
    	if(j+1 < col && board[i][j+1] == 'O')solve_border(board,i,j+1,row,col);
    }
    void solve(vector<vector<char> > &board) {
    	int row = board.size();
    	if(row <= 0)return;
    	int col = board[0].size();
    	int i,j;
    	for(j = 0;j < col;j++)
    	{
    		if(board[0][j] == 'O')solve_border(board,0,j,row,col);
    		if(board[row-1][j] == 'O')solve_border(board,row-1,j,row,col);
    	}
    	for(i = 0;i < row;i++)
    	{
    		if(board[i][col-1] == 'O')solve_border(board,i,col-1,row,col);
    		if(board[i][0] == 'O')solve_border(board,i,0,row,col);
    	}
    	for(i = 1; i < row;i++)
    	{
    		for(j = 1;j < col;j++)
    		{
    			if(board[i][j] == 'O')board[i][j] = 'X';
    		}
    	}
    	for(i = 0; i< row;i++)
    	{
    		for(j = 0;j < col;j++)
    		{
    			if(board[i][j] == 'A')board[i][j] = 'O';
    		}
    	}
    }
};

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

click to show follow up.

class Solution {
public:
    void setZeroes(vector<vector<int> > &matrix) 
    {
    	int rows = matrix.size();
    	if(rows <= 0)return;
    	int cols = matrix[0].size();
    	if(cols <= 0)return;
    	int i,j;
    	bool row0 = false,col0 = false;
    	for(j = 0;j < cols;++j)//判断第一行是否有0
    	{
    		if(matrix[0][j]==0)
    		{
    			row0 = true;
    			break;
    		}
    	}
    	for(i = 0;i < rows;++i)//判断第一列是否有0
    	{
    		if(matrix[i][0]==0)
    		{
    			col0 = true;
    			break;
    		}
    	}
    	for(i = 1;i < rows;++i)
    	{
    		for(j = 1;j < cols;++j)
    		{
    			if(matrix[i][j] == 0)
    			{
    				matrix[i][0] = matrix[0][j] = 0;//记录在第一行和第一列
    			}
    		}
    	}
    	for(j = 1; j < cols;++j)
    	{
    		if(matrix[0][j] == 0)//把第j列设置为0
    		{
    			for(i = 0;i < rows;++i)matrix[i][j] = 0;
    		}
    	}
    	for(i = 1;i < rows;++i)
    	{
    		if(matrix[i][0] == 0)//把第i行设置为0
    		{
    			for(j = 0;j < cols;++j)matrix[i][j] = 0; 
    		}
    	}
    	if(row0)
    	{
    		for(j = 0;j < cols;++j)matrix[0][j] = 0;
    	}
    	if(col0)
    	{
    		for(i = 0;i < rows;++i)matrix[i][0] = 0;
    	}
    }
};

leetcode 之 Surrounded Regions

标签：matrix   矩阵   leetcode   

原文地址：http://blog.csdn.net/fangjian1204/article/details/38895467