hdu1010 扩展KMP求字符串最小循环节

2019年3月17日 252次阅读 来源: KMP算法

Problem:扩展kmp求字符串最小循环节
Analyse:
字符串循环节等于字符串最长前缀后缀减去这个前缀后缀中间交的长度。

/**********************jibancanyang************************** *Author* :jibancanyang *Created Time* : 六 5/ 7 21:17:06 2016 *File Name* : hdu1010.cpp **Code**: ***********************1599664856@qq.com**********************/

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <stack>
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;
vector<int> vi;
#define pr(x) cout << #x << ": " << x << " " 
#define pl(x) cout << #x << ": " << x << endl;
#define pri(a) printf("%d\n",(a));
#define xx first
#define yy second
#define sa(n) scanf("%d", &(n))
#define sal(n) scanf("%lld", &(n))
#define sai(n) scanf("%I64d", &(n))
#define vep(c) for(decltype((c).begin() ) it = (c).begin(); it != (c).end(); it++) 
const int mod = int(1e9) + 7, INF = 0x3fffffff;
const int maxn = 1e6 + 13;
char t[maxn], s[maxn];
int nexts[maxn], extend[maxn], slen, tlen;

//计算next数组，保存到next参数中。
void getextendnexts(void)
{
    tlen = strlen(t), slen = strlen(s);
    for (int i = 1, j = -1, a, p; i < tlen; i++, j--)
        if (j < 0 || i + nexts[i - a] >= p) {
            if (j < 0)  j = 0, p = i;
            while (p < tlen && t[j] == t[p]) j++, p++;
            nexts[i] = j, a = i;
        }
        else nexts[i] = nexts[i - a];
}

void getextend (void)
{
    getextendnexts();  //计算next数组。mx是表示最大长度的常数。
    for (int i = 0, j = -1, a, p; i < slen; i++, j--)
        if (j < 0 || i + nexts[i - a] >= p) {
            if (j < 0)  j = 0, p = i;
            while (p < slen && j < tlen && s[p] == t[j]) j++, p++;
            extend[i] = j, a = i;
        }
        else extend[i] = nexts[i - a];
}


int main(void)
{
#ifdef LOCAL
   // freopen("/Users/zhaoyang/in.txt", "r", stdin);
    //freopen("/Users/zhaoyang/out.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    while (~scanf("%s", s)) {
        memcpy(t, s, sizeof(s));
        getextend();
        int ans = slen;
        for (int i = 1; i < slen; i++) {
            if (extend[i] == slen - i) {
                ans = i;
                break;
            }
        }
        pri(ans);
    }

    return 0;
}
    原文作者：KMP算法
    原文地址: https://blog.csdn.net/jibancanyang/article/details/51340155
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
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