HDU-1496-Equations && POJ-1840-Eqs （hash）

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HDU1494：

a*x1^2+b*x2^2+c*x3^2+d*x4^2=0

分块HASH:O（N^4）->O(N^2+N^2)

POJ1840：

a1x1³+ a2x2³+ a3x3³+ a4x4³+ a5x5³=0

分块HASH:O（N^5）->O(N^2+N^3)

HDU 1496：

//#include <bits/stdc++.h>#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <vector>#include <algorithm>#define INF 0x3f3f3f3fusing namespace std;const int MAXN = 0.4e7+7;const int P = 0.1e7;int hash_[MAXN];int main(){    int a[4];    while(scanf("%d%d%d%d",&a[0],&a[1],&a[2],&a[3])!=EOF)    {        if(a[0]*a[1]>0 && a[2]*a[3]>0 && a[1]*a[2]>0){printf("0\n");continue;}        memset(hash_,0,sizeof(hash_));        int f=0;        for(int i=1; i<=100; ++i)            for(int j=1; j<=100; ++j)            hash_[ i*i*a[0]+j*j*a[1]+P ]++;        int ans=0;        for(int i=1; i<=100; ++i)            for(int j=1; j<=100; ++j)            ans+=hash_[ P-i*i*a[2]-j*j*a[3] ];        printf("%d\n",ans*16);    }    return 0;}

POJ 1840：

//#include <bits/stdc++.h>#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <vector>#include <algorithm>#define INF 0x3f3f3f3fusing namespace std;const int MAXN = 0.25e8+7;const int P = 0.25e8;short hash_[MAXN];int main(){    int a[5];    while(scanf("%d%d%d%d%d",&a[0],&a[1],&a[2],&a[3],&a[4])!=EOF)    {        memset(hash_,0,sizeof(hash_));        for(int i=-50; i<=50; ++i)if(i!=0)            for(int j=-50; j<=50; ++j)            {                if(j==0)continue;                int f=i*i*i*a[0]+j*j*j*a[1];                f=-f;                if(f<0)f+=P;                hash_[f]++;            }        int ans=0;        for(int i=-50; i<=50; ++i)if(i!=0)            for(int j=-50; j<=50; ++j)if(j!=0)                for(int k=-50; k<=50; ++k)                {                    if(k==0)continue;                    int f=i*i*i*a[2]+j*j*j*a[3]+k*k*k*a[4];                    if(f<0)f+=P;                    ans+=hash_[f];                }        printf("%d\n",ans);    }    return 0;}//37 29 41 43 47

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