hdu 3374 String Problem (字符串最小最大表示 + KMP求循环节)

Problem - 3374

 

KMP求循环节。

http://www.cnblogs.com/wuyiqi/archive/2012/01/06/2314078.html

 

　　循环节推导的证明相当的好，这题是很裸的套算法的题。

代码如下：

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 1111111;
char buf[N];
int next[N];

void getNext(char *str) {
    char *si = str;
    int *ni = next;
    int j = *next = -1;
    while (*si) {
        while (j > -1 && *si != *(str + j)) j = *(next + j);
        si++, ni++, j++;
//        if (*si == *(str + j)) *ni = *(next + j);
//        else *ni = j;
        *ni = j;
    }
}

int minMaxExp(char *s, bool mini) {
    int i = 0, j = 1, k = 0, t;
    int len = strlen(s);
    while (i < len && j < len && k < len) {
//        cout << i << ' ' << j << ' ' << k << endl;
        t = s[(i + k) % len] - s[(j + k) % len];
        if (!t) k++;
        else {
            if (mini ^ (t > 0)) j += k + 1;
            else i += k + 1;
            if (i == j) j++;
            k = 0;
        }
    }
    return min(i, j);
}

int main() {
    while (cin >> buf) {
        getNext(buf);
//        for (int i = 0, sz = strlen(buf); i < sz; i++) cout << next[i] + 1 << ' '; cout << endl;
        int cycle = strlen(buf);
//        cout << "got next" << endl;
        cycle /= (cycle - next[cycle - 1] - 1);
        cout << minMaxExp(buf, true) + 1 << ' ' << cycle << ' ' << minMaxExp(buf, false) + 1 << ' ' << cycle << endl;
    }
    return 0;
}

 

——written by Lyon