POJ 3274.Gold Balanced Lineup

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题目:http://poj.org/problem?id=3274

AC代码(C++):

#include <iostream>#include <algorithm>#include <stdio.h>#include <vector>#include <queue>#include <math.h>#include <string>#include <string.h>#include <bitset>#define INF 0xfffffff#define MAXN 100005#define prime 99991using namespace std;struct NODE{int num;int next;};NODE node[MAXN];int hash[MAXN];int n,k,cnt;int feature[MAXN][31];int sum[MAXN][31];int c[MAXN][31];bool cmp(int a, int b){for(int i = 0; i < k; i++){if(c[a][i]!=c[b][i])return false;}return true;}int getHash(int num){int rtn = 0;for(int i = 0; i < k; i++){rtn += (c[num][i]*i)%prime;}return abs(rtn)%prime;}void insertHash(int num, int key){node[cnt].num = num;node[cnt].next = hash[key];hash[key] = cnt;cnt++;}int searchHash(int num){int key = getHash(num);int next = hash[key];while(next!=-1){if(!cmp(num,node[next].num)){next = node[next].next;}else return node[next].num;}insertHash(num,key);return -1;}int main(){cin>>n>>k;cnt = 0;for(int i = 0; i < prime; i++)hash[i] = -1;for(int i = 0; i < k; i++)c[0][i] = 0;searchHash(0);int maxlen = 0;for(int i = 0; i < n; i++){int tmp;cin>>tmp;for(int j = 0; j < k; j++){feature[i+1][j] = tmp%2;tmp/=2;}if(i==0){for(int j = 0; j < k; j++)sum[1][j] = feature[1][j];}else{for(int j = 0; j < k; j++)sum[i+1][j] = sum[i][j]+feature[i+1][j];}for(int j = 0; j < k; j++)c[i+1][j] = sum[i+1][j]-sum[i+1][0];int index = searchHash(i+1);if(index!=-1&&i+1-index>maxlen)maxlen=i+1-index;}cout<<maxlen;}

总结: 把问题转换成哈希查找就好做了, 具体转换参照官方解题报告, 具体做法看这里:

http://www.cnblogs.com/lyy289065406/archive/2011/07/30/2122224.html

转换好了后就是普通的数字哈希了.

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