UVA 11464 偶數矩陣

這是白皮書上的一道例題

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#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn = 20;
const int INF = 2147483647;

int n,A[maxn][maxn],B[maxn][maxn];

int check(int s)
{
    memset(B,0,sizeof(B));
    for(int c = 0; c < n ; c++)
    {
        if(s&(1<<c))B[0][c] = 1;
        else if(A[0][c] == 1)return INF;
    }
    for(int r = 1; r < n ; r++ )
        for(int c = 0; c < n ; c++)
        {
            int sum = 0;
            if(r > 1)sum += B[r-2][c];
            if(c > 0)sum += B[r-1][c-1];
            if(c < n-1)sum += B[r-1][c+1];
            B[r][c] = sum%2;
            if(A[r][c]==1&&B[r][c]==0)return INF;
        }
    int cnt = 0;
    for(int r = 0; r < n; r++ )
        for(int c = 0 ; c < n ; c++)
            if(A[r][c]!=B[r][c])cnt++;
    return cnt;
 } 

int main()
{
    int T;
    scanf("%d",&T);
    for(int kase = 1 ; kase <= T ; kase++ )
    {
        scanf("%d",&n);
        for(int r0 = 0 ; r0 < n; r0++ )
            for(int c0 = 0; c0 < n; c0++ )
                scanf("%d",&A[r0][c0]);

        int ans = INF;
        for(int s = 0; s < (1<<n) ; s++ )
            ans = min(ans,check(s));
        if(ans==INF)ans=-1;
        printf("Case %d: %d",kase,ans);

    }
    return 0;
 }