uva 1152 4 Values whose Sum is 0(二分_中途相遇|| hash)

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hash

#include<cstdio>#include<iostream>#include<map>#include<vector>using namespace std;const int maxn=4005;int a[maxn],b[maxn],c[maxn],d[maxn];struct Hash_map{    static const int mask=0x7fffff;    int p[8388608],q[8388608];    void clear()  //初始化为0    {        for(int i=0; i<=mask; ++i)            q[i]=0;    }    int& operator [](int k)  //重载“[]”    {        int i;        for(i=k&mask; q[i]&&p[i]!=k; i=(i+1)&mask);            p[i]=k;        return q[i];    }}hash;int main(){int t,i,j,n;scanf("%d",&t);while(t--) {scanf("%d",&n);for(i=0;i<n;i++) {scanf("%d%d%d%d",&a[i],&b[i],&c[i],&d[i]);}hash.clear();for(i=0;i<n;i++) {for(j=0;j<n;j++) {hash[a[i]+b[j]]++;}}int sum=0;for(i=0;i<n;i++) {for(j=0;j<n;j++) {sum+=hash[-c[i]-d[j]];}}printf("%d\n",sum);if(t) printf("\n");}return 0;}

二分_stl

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;const int maxn=4005;int a[maxn],b[maxn],c[maxn],d[maxn],s1[maxn*maxn],s2[maxn*maxn];int main(){int t,n,i,j;scanf("%d",&t);for(int z=1;z<=t;z++) {scanf("%d",&n);for(i=0;i<n;i++) {scanf("%d%d%d%d",&a[i],&b[i],&c[i],&d[i]);}int k1=0,k2=0;for(i=0;i<n;i++) {for(j=0;j<n;j++){    s1[k1++]=a[i]+b[j];        s2[k2++]=c[i]+d[j];        }}sort(s2,s2+k2);int sum=0;for(i=0;i<k1;i++) {sum+=upper_bound(s2,s2+k2,-s1[i])-lower_bound(s2,s2+k2,-s1[i]);}printf("%d\n",sum);if(z!=t) printf("\n");}return 0;}

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