POJ 2785 4 Values whose Sum is 0

用hash写了一遍，hash的空间复杂度不是盖的

/*Accepted 176460K 3907MS C++ 1006B 2012-05-25 09:13:41 */
#include<cstdio>
#include<cstring>
#include<cstdlib>
#define cal(x) ( (x + (1 << 29 | 1) * M) % MAX)
#define LL __int64
const int MAX = 20000001;
const int M = 17531753;
const int MAXN = 4005;
int hash[MAX], cnt[MAX];
bool vis[MAX];
int a[MAXN],b[MAXN], c[MAXN], d[MAXN];
void inhash( int x)
{
    LL t = x;
    t = cal(t);
    while( vis[t] && hash[t] != x)
        t = cal(t);
    if( !vis[t] ) {vis[t] = true; cnt[t] = 1; hash[t] = x;}
    else cnt[t] ++;
}

int find( int x)
{
    LL t = x;
    t = cal(t);
    while( vis[t] && hash[t] != x)
        t = cal(t);
    if( vis[t]) return cnt[t];
    return 0;
}

int main()
{
    int n;
    while( scanf( "%d", &n) == 1)
    {
        for( int i = 0; i < n; i ++)
            scanf( "%d%d%d%d", &a[i], &b[i], &c[i], &d[i]);
        for( int i = 0; i < n; i ++)
            for( int j = 0; j < n; j ++)
                inhash( a[i] + b[j]);
        int ans = 0;
        for( int i = 0; i < n; i ++)
            for( int j = 0; j < n; j ++)
                ans += find( -(c[i] + d[j] ));
        printf( "%d\n", ans);
    }
    return 0;
}