hdu 1496 Equations

http://acm.hdu.edu.cn/showproblem.php?pid=1496

　　上一题hash的升级版，不过还是简单题..只能当作是练手了...

#include <cstdio>
#include <cstring>
#include <cstdlib>

const int maxn = 50007;
int hash[maxn], cnt[maxn];
int tx[101];

void pre(){
    for (int i = 1; i <= 100; i++){
        tx[i] = i * i;
    }
}

void init(){
    memset(cnt, 0, sizeof(cnt));
}

void insert(int a){
    int p = (a << 3) % maxn;

    if (p < 0) p += maxn;
    while (hash[p] != a && cnt[p]) p = (p + 1) % maxn;
    hash[p] = a;
    cnt[p]++;
}

int count(int a){
    int p = (a << 3) % maxn;

    if (p < 0) p += maxn;
    while (hash[p] != a && cnt[p]) p = (p + 1) % maxn;

    return cnt[p];
}

int main(){
    int a, b, c, d;

    pre();
    while (~scanf("%d%d%d%d", &a, &b, &c, &d)){
        init();
        if ((a < 0 && b < 0 && c < 0 && d < 0) || (a > 0 && b > 0 && c > 0 && d > 0)){
            puts("0");
            continue;
        }
        for (int i = 1; i <= 100; i++){
            for (int j = 1; j <= 100; j++){
                insert(a * tx[i] + b * tx[j]);
            }
        }
        int tt = 0;

        for (int i = 1; i <= 100; i++){
            for (int j = 1; j <= 100; j++){
                tt += count(- (c * tx[i] + d * tx[j]));
            }
        }
        printf("%d\n", tt << 4);
    }

    return 0;
}

——written by Lyon