POJ 3274 Gold Balanced Lineup 哈希

题目链接： http://poj.org/problem?id=3274

#include <stdio.h>
#include <string.h>
#include <algorithm>

bool feature[100001][30];
int sum[100001][30], c[100001][30], n, k;
const int prime = 99991;

struct hash_table
{
    int flag;
    struct hash_table *next;
}*Hash[prime];

int hash_insert(int key, int flag)
{
    if(Hash[key] == NULL)
    {
        Hash[key] = new hash_table;
        Hash[key]->flag = flag;
        Hash[key]->next = NULL;
        return 0;
    }
    struct hash_table *p = Hash[key];
    while(p->next != NULL)
    {
        bool ok = 1;
        for(int i = 0; i < k; i++)
        {
            if(c[p->flag][i] != c[flag][i])
            {
                ok = 0;
                break;
            }
        }
        if(ok)return flag - p->flag;
        p = p->next;
    }
    for(int i = 0; i < k; i++)
    {
        if(c[p->flag][i] != c[flag][i])
        {
            p->next = new hash_table;
            p->next->flag = flag;
            p->next->next = NULL;
            return 0;
        }
    }
    return flag - p->flag;
}

int main()
{
    int x;
    while(scanf("%d %d", &n, &k) != EOF)
    {
        memset(Hash, 0, sizeof(Hash));
        for(int i = 1; i <= n; i++)
        {
            scanf("%d", &x);
            for(int j = 0; j < k; j++)
                feature[i][j] = (x >> j) & 1;
        }
        memset(sum[0], 0, sizeof(sum[0]));
        memset(feature[0], 0, sizeof(feature[0]));
        int ans = 0;
        hash_insert(0, 0);
        for(int i = 1; i <= n; i++)
        {
            int key = 0;
            for(int j = 0; j < k; j++)
            {
                sum[i][j] = sum[i-1][j] + feature[i][j];
                c[i][j] = sum[i][j] - sum[i][0];
                key += c[i][j] * j;
            }
            ans = std::max(ans, hash_insert(std::abs(key)%prime, i));
        }
        printf("%d
", ans);
    }
    return 0;
}