UVA 601: The Path

#include <stdio.h>
#include <string.h>
char g[105][105];
int used[105][105], n;
void dfs(int x, int y, int w) {
if(x < 0 || y < 0 || x >= n || y >= n)
return ;
if(used[x][y] || g[x][y] != w)
return ;
used[x][y] = 1;
dfs(x+1, y, w);
dfs(x-1, y, w);
dfs(x, y+1, w);
dfs(x, y-1, w);
}
int main() {
int i, j, p, q;
while(scanf("%d", &n) == 1 && n) {
memset(used, 0, sizeof(used));
for(i = 0; i < n; i++)
scanf("%s", g[i]);
for(i = 0; i < n; i++) {
if(g[i][0] == 'W')
dfs(i, 0, 'W');
if(g[0][i] == 'B')
dfs(0, i, 'B');
}
int Wwin = 0, Bwin = 0;
for(i = 0; i < n; i++) {
if(used[i][n-1] && g[i][n-1] == 'W')
Wwin = 1;
if(used[n-1][i] && g[n-1][i] == 'B')
Bwin = 1;
}
if(Wwin) {
puts("White has a winning path.");
continue;
}
if(Bwin) {
puts("Black has a winning path.");
continue;
}
for(i = 0; i < n; i++) {
for(j = 0; j < n; j++) {
if(g[i][j] == 'U' && !Wwin) {
memset(used, 0, sizeof(used));
g[i][j] = 'W';
for(p = 0; p < n; p++)
if(g[p][0] == 'W')
dfs(p, 0, 'W');
for(p = 0; p < n; p++)
if(used[p][n-1] && g[p][n-1] == 'W')
Wwin = 1;
g[i][j] = 'U';
}
}
}
if(Wwin) {
puts("White can win in one move.");
continue;
}
for(i = 0; i < n; i++) {
for(j = 0; j < n; j++) {
if(g[i][j] == 'U' && !Bwin) {
memset(used, 0, sizeof(used));
g[i][j] = 'B';
for(p = 0; p < n; p++)
if(g[0][p] == 'B')
dfs(0, p, 'B');
for(p = 0; p < n; p++)
if(used[n-1][p] && g[n-1][p] == 'B')
Bwin = 1;
g[i][j] = 'U';
}
}
}
if(Bwin) {
puts("Black can win in one move.");
continue;
}
puts("There is no winning path.");
}
return 0;
}