POJ 1659 Frogs' Neighborhood

　　题目大意：判断一个序列是否可图化。Havel-Hakimi定理的简单应用。

　　在看D_Double's Journey的关于Havel-Hakimi定理时提到这道题，就做了一下。可悲的是，因为一些小细节问题WA了两次，无语...

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAXN 12

struct Vertex
{
    int d, id;
    bool operator < (const Vertex& v) const
    {
        return d > v.d;
    }
};
Vertex vertex[MAXN];
int G[MAXN][MAXN], n;

bool Havel_Hakimi()
{
    for (int i = 0; i < n-1; i++)
    {
        sort(vertex+i, vertex+n);
        if (i + vertex[i].d >= n)  return false;
        int x = vertex[i].id;
        for (int j = i+1; j <= i+vertex[i].d; j++)
        {
            vertex[j].d--;
            int y = vertex[j].id;
            G[x][y] = G[y][x] = 1;
            if (vertex[j].d < 0)  return false;
        }
    }
    if (vertex[n-1].d)  return false;
    return true;
}

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int T;
    scanf("%d", &T);
    while (T--)
    {
        scanf("%d", &n);
        for (int i = 0; i < n; i++)
        {
            scanf("%d", &vertex[i].d);
            vertex[i].id = i;
        }
        memset(G, 0, sizeof(G));
        if (Havel_Hakimi())  
        {
            printf("YES
");
            for (int i = 0; i < n; i++)
                for (int j = 0; j < n; j++)
                    printf("%d%s", G[i][j], (j == n-1) ? "
" : " ");
        }
        else  printf("NO
");
        if (T)  printf("
");
    }
    return 0;
}