hdu 1186(搜索+HASH)

/*
6
150
1  2
-1  2
1  2
-1  2
1  2
-1  2
*/
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<math.h>
#include<queue>
#include<iostream>
using namespace std;
const int INF = 999999999;
const int N = 151*151*151;
int k[10],p[10];
int n,m,cnt,mid;
/*************构造HASH表****************/
bool used[N];
struct Hash{
    int val;
    int cnt;
}HashTable[N];
void initHash(){
    memset(used,false,sizeof(used));
    memset(HashTable,0,sizeof(HashTable));
}
int SearchHash(int v)
{
    int temp = v;
    while(temp<0) temp+=N;
    while(temp>=N) temp-=N;
    while(used[temp]&&HashTable[temp].val!=v){
        temp++;
        if(temp>=N) temp-=N;
     }
    return temp;
}
void InsertHash(int v)
{
    int pos = SearchHash(v);
    HashTable[pos].val = v;
    used[pos] = true;
    HashTable[pos].cnt++;
}
/*****************************************/
int pow(int a,int n)
{
    int ans = 1;
    while(n)
    {
        if(n&1) ans = ans*a;
        a = a*a;
        n>>=1;
    }
    return ans;
}
void dfs(int step,int ans)
{
    if(step==mid)
    {
        InsertHash(ans);
        return ;
    }
    else
    {
        for(int i=1; i<=m; i++)
        {
            dfs(step+1,ans + k[step]*pow(i,p[step]));
        }
    }
}
void dfs2(int step,int ans)
{
    if(step==n+1)
    {
        ans = -ans;
        int s = SearchHash(ans);
        if(HashTable[s].val == ans){
            cnt+=HashTable[s].cnt;
        }
        return ;
    }
    else
    {
        for(int i=1; i<=m; i++)
        {
            dfs2(step+1,ans + k[step]*pow(i,p[step]));
        }
    }
}
int main()
{

    while(scanf("%d%d",&n,&m)!=EOF)
    {
        initHash();
        cnt = 0;
        for(int i=1; i<=n; i++)
        {
            scanf("%d%d",&k[i],&p[i]);
        }
        if(n==1){
            printf("%d\n",0);
            continue;
        }
        mid = n/2+1;
        dfs(1,0);
        dfs2(mid,0);
        printf("%d\n",cnt);
    }
    return 0;
}