Uva 11464 Even Parity

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 16;
const int INF = 2100000000 / 2;

int mat[maxn][maxn],ans,n;

int getsum(int x,int y,int m[maxn][maxn]) {
int ans = 0;
if(x > 1) ans += m[x - 1][y];
if(x < n) ans += m[x + 1][y];
if(y > 1) ans += m[x][y - 1];
if(y < n) ans += m[x][y + 1];
return ans;
}

int check() {
int matA[maxn][maxn],ret = 0;
for(int i = 1;i <= n;i++) {
for(int j = 1;j <= n;j++) {
matA[i][j] = mat[i][j];
}
}
for(int i = 1;i <= n;i++) {
for(int j = 1;j <= n;j++) {
if(getsum(i,j,matA) & 1) {
if(i == n || matA[i + 1][j] == 1) {
return INF;
} else {
matA[i + 1][j] = 1;
ret++;
}
}
}
}
return ret;
}

void dfs(int pos,int ch) {
if(pos > n) return;
ans = min(check() + ch,ans);
dfs(pos + 1,ch);
if(mat[1][pos] == 0) {
mat[1][pos] = 1;
ans = min(ans,check() + ch + 1);
dfs(pos + 1,ch + 1);
mat[1][pos] = 0;
}
}

int main() {
int T; scanf("%d",&T);
for(int kase = 1;kase <= T;kase++) {
scanf("%d",&n);
for(int i = 1;i <= n;i++) {
for(int j = 1;j <= n;j++) {
scanf("%d",&mat[i][j]);
}
}
ans = INF;
dfs(1,0);
printf("Case %d: ",kase);
if(ans == INF) {
puts("-1");
} else {
printf("%d\n",ans);
}
}
return 0;
}