Gold Balanced Lineup(hash)

http://poj.org/problem?id=3274

*****

#include <stdio.h>
#include <iostream>
#include <string.h>
#include <stdlib.h>
using namespace std;
const int N=100001;
const int MOD=99991;
int Maxdis,k;
int c[N][32],sum[N][32];
int vis[N][32];

struct node
{
    int row_i;
    struct node *next;
}*hash[N];
bool cmp(int a1,int b1)
{
    for (int i = 0; i < k; i++)
    {
        if (c[a1][i]!=c[b1][i])
            return false;
    }
    return true;
}
void Hash(int row_i)
{
    int key = 0,i = 0;
    while(i < k)
    {
        key = key*131+c[row_i][i];
        i++;
    }
    key=abs(key)%MOD;
    if (!hash[key])
    {
        hash[key] = new node;
        hash[key]->row_i = row_i;
        hash[key]->next = NULL;
    }
    else
    {
        struct node *p = hash[key];
        if(cmp(p->row_i,row_i))
        {
            if (Maxdis < row_i-(p->row_i))
                Maxdis = row_i-(p->row_i);
            return ;
        }
        while(p->next)
        {
            if (cmp(p->next->row_i,row_i))
            {
                if (Maxdis < row_i-(p->next->row_i))
                    Maxdis = row_i-(p->next->row_i);
                return ;
            }
            p = p->next;
        }
        p->next = new node;
        p->next->row_i = row_i;
        p->next->next = NULL;
    }
    return ;
}
int main()
{
    int n;
    scanf("%d %d",&n,&k);
    for (int i = 0; i < k; i++)
    {
        c[0][i] = 0;
        sum[0][i] = 0;
    }
    memset(hash,0,sizeof(hash));
    Hash(0);
    Maxdis = 0;
    for (int i = 1; i <= n; i++)
    {
        int num;
        scanf("%d",&num);
        for (int j = 0; j < k; j++)
        {
            vis[i][j]=num%2;
            num/=2;
            sum[i][j] = sum[i-1][j]+vis[i][j];
            c[i][j] = sum[i][j]-sum[i][0];
        }
        Hash(i);
    }
    printf("%d
",Maxdis);
    return 0;
}