leetcode surrounded-regions
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(vector<vector<char> > &board)
{
int x = board.size();
if (0 == x)
return;
int y = board[0].size();
vector<vector<int> >flag (x, vector<int> (y, -1)); //0是 1不是 -1 未判定 2寻找中
for(int i=1;i<x-1;i++)
for (int j=1;j<y-1;j++)
if (board[i][j] == 'O' && flag[i][j] == -1)
judge(board, flag, i, j);
for(int i=1;i<x;i++)
for (int j=1;j<y;j++)
if (flag[i][j] == 0)
board[i][j] = 'X';
}
void judge(vector<vector<char> > &board, vector<vector<int> > &flag, int i, int j)
{
vector<pair<int, int> > allO;
int res = findallO(board, allO, flag, i, j)?0:1;
for (int k=0;k<allO.size();k++)
{
if(flag[allO[k].first][allO[k].second] != 0 && flag[allO[k].first][allO[k].second] != 1)
flag[allO[k].first][allO[k].second] = res;
}
}
bool findallO(vector<vector<char> > &board, vector<pair<int, int> > &allO, vector<vector<int> > &flag, int i, int j)
{
if (i == 0 || j == 0 || i == board.size()-1 || j == board[0].size()-1)
return false;
bool res = true;
allO.push_back(pair<int,int>(i,j));
flag[i][j] = 2;
if (board[i-1][j] == 'O' && flag[i-1][j] == -1)
res = res & findallO(board, allO, flag, i-1, j);
if (board[i+1][j] == 'O' && flag[i+1][j] == -1)
res = res & findallO(board, allO, flag, i+1, j);
if (board[i][j-1] == 'O' && flag[i][j-1] == -1)
res = res & findallO(board, allO, flag, i, j-1);
if (board[i][j+1] == 'O' && flag[i][j+1] == -1)
res = res & findallO(board, allO, flag, i, j+1);
return res;
}
};
//网上的思路 从四周的"O"开始 将所有联通的“O”变为“a” 最后剩下的“O”变为“X” “a”变为“O”
class Solution {
public:
void solve(vector<vector<char> > &board)
{
int x = board.size();
if (0 == x)
return;
int y = board[0].size();
for(int i=0;i<x;i++)
for (int j=0;j<y;j++)
if (board[i][j] == 'O' && (i == 0 || j == 0 || i == x-1 || j == y-1))
DFS(board, i, j);
for (int i = 0; i < board.size(); ++i)
{
for (int j = 0; j < board[i].size(); ++j)
{
if (board[i][j] == 'O') board[i][j] = 'X';
if (board[i][j] == 'a') board[i][j] = 'O';
}
}
}
void DFS(vector<vector<char> > &board, int i, int j)
{
board[i][j] = 'a';
if (i>0 && board[i-1][j] == 'O')//>0或1都行
DFS(board,i-1, j);
if (i<board.size()-1 && board[i+1][j] == 'O')
DFS(board, i+1, j);
if (j>0 && board[i][j-1] == 'O')//>0或1都行
DFS(board, i, j-1);
if (j<board[0].size()-1 && board[i][j+1] == 'O' )
DFS(board, i, j+1);
}
};
测试
#include"head.h"
class Solution1 {
public:
void solve(vector<vector<char> > &board)
{
int x = board.size();
if (0 == x)
return;
int y = board[0].size();
vector<vector<int> >flag (x, vector<int> (y, -1)); //0是 1不是 -1 未判定 2寻找中
for(int i=1;i<x-1;i++)
for (int j=1;j<y-1;j++)
if (board[i][j] == 'O' && flag[i][j] == -1)
judge(board, flag, i, j);
for(int i=1;i<x;i++)
for (int j=1;j<y;j++)
if (flag[i][j] == 0)
board[i][j] = 'X';
}
void judge(vector<vector<char> > &board, vector<vector<int> > &flag, int i, int j)
{
vector<pair<int, int> > allO;
int res = findallO(board, allO, flag, i, j)?0:1;
for (int k=0;k<allO.size();k++)
{
if(flag[allO[k].first][allO[k].second] != 0 && flag[allO[k].first][allO[k].second] != 1)
flag[allO[k].first][allO[k].second] = res;
}
}
bool findallO(vector<vector<char> > &board, vector<pair<int, int> > &allO, vector<vector<int> > &flag, int i, int j)
{
if (i == 0 || j == 0 || i == board.size()-1 || j == board[0].size()-1)
return false;
bool res = true;
allO.push_back(pair<int,int>(i,j));
flag[i][j] = 2;
if (board[i-1][j] == 'O' && flag[i-1][j] == -1)
res = res & findallO(board, allO, flag, i-1, j);
if (board[i+1][j] == 'O' && flag[i+1][j] == -1)
res = res & findallO(board, allO, flag, i+1, j);
if (board[i][j-1] == 'O' && flag[i][j-1] == -1)
res = res & findallO(board, allO, flag, i, j-1);
if (board[i][j+1] == 'O' && flag[i][j+1] == -1)
res = res & findallO(board, allO, flag, i, j+1);
return res;
}
};
class Solution {
public:
void solve(vector<vector<char> > &board)
{
int x = board.size();
if (0 == x)
return;
int y = board[0].size();
for(int i=0;i<x;i++)
for (int j=0;j<y;j++)
if (board[i][j] == 'O' && (i == 0 || j == 0 || i == x-1 || j == y-1))
DFS(board, i, j);
for (int i = 0; i < board.size(); ++i)
{
for (int j = 0; j < board[i].size(); ++j)
{
if (board[i][j] == 'O') board[i][j] = 'X';
if (board[i][j] == 'a') board[i][j] = 'O';
}
}
}
void DFS(vector<vector<char> > &board, int i, int j)
{
board[i][j] = 'a';
if (i>0 && board[i-1][j] == 'O')
DFS(board,i-1, j);
if (i<board.size()-1 && board[i+1][j] == 'O')
DFS(board, i+1, j);
if (j>0 && board[i][j-1] == 'O')
DFS(board, i, j-1);
if (j<board[0].size()-1 && board[i][j+1] == 'O' )
DFS(board, i, j+1);
}
};
/*
OOOOXX,
OOOOOO,
OXOXOO,
OXOOXO,
OXOXOO,
OXOOOO
[OOOOXX,OOOOOO,OXOXOO,OXOOXO,OXOXOO,OXOOOO]
[OOOOXX,OOOOOO,OXOXOO,OXOOXO,OXOXOO,OXOOOO]
[OOOOXX,OOOOOO,OXOXOO,OXOXXO,OXOXOO,OXOOOO]*/
int main()
{
Solution s;
vector<vector<char> > board;
char A[] = {'O', 'O', 'O', 'O', 'X', 'X'};
vector<char> tmp1(A, A+6);
board.push_back(tmp1);
char B[] = {'O', 'O', 'O', 'O','O', 'O'};
vector<char> tmp2(B, B+6);
board.push_back(tmp2);
char C[] = {'O', 'X', 'O', 'X','O', 'O'};
vector<char> tmp3(C, C+6);
board.push_back(tmp3);
char D[] = {'O', 'X', 'O', 'O','X', 'O'};
vector<char> tmp4(D, D+6);
board.push_back(tmp4);
char E[] = {'O', 'X', 'O', 'X','O', 'O'};
vector<char> tmp5(E, E+6);
board.push_back(tmp5);
char F[] = {'O', 'X', 'O', 'O','O', 'O'};
vector<char> tmp6(F, F+6);
board.push_back(tmp6);
print2Dvectorint(board);
cout<<endl;
s.solve(board);
print2Dvectorint(board);
}