POJ2752——Seek the Name, Seek the Fame

Seek the Name, Seek the Fame

Description

The little cat is so famous, that many couples tramp over hill and dale to Byteland, and asked the little cat to give names to their newly-born babies. They seek the name, and at the same time seek the fame. In order to escape
from such boring job, the innovative little cat works out an easy but fantastic algorithm:

Step1. Connect the father‘s name and the mother‘s name, to a new string S.

Step2. Find a proper prefix-suffix string of S (which is not only the prefix, but also the suffix of S).

Example: Father=‘ala‘, Mother=‘la‘, we have S = ‘ala‘+‘la‘ = ‘alala‘. Potential prefix-suffix strings of S are {‘a‘, ‘ala‘, ‘alala‘}. Given the string S, could you help the little cat to write a program to calculate the length of possible prefix-suffix strings
of S? (He might thank you by giving your baby a name:)

Input

The input contains a number of test cases. Each test case occupies a single line that contains the string S described above.

Restrictions: Only lowercase letters may appear in the input. 1 <= Length of S <= 400000.

Output

For each test case, output a single line with integer numbers in increasing order, denoting the possible length of the new baby‘s name.

Sample Input

ababcababababcabab
aaaaa

Sample Output

2 4 9 18
1 2 3 4 5

KMP 算法next数组的应用， 寻找所有可能的公共前后缀，我们先对整个串求一个next数组，（未优化的next数组相当于每个字符之前存在的最长的公共前后缀长度-1）

然后去“截”这个串，每次截的位置是next[len - 1]，len是未截之前字符串长度，一开始为整个字符串长度

#include <map>
#include <set>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 400010;
char str[N];
int next[N];
int ans[N];

void get_next()
{
	int len = strlen(str);
	int j = 0, k = -1;
	next[0] = -1;
	while (j < len - 1)
	{
		if (k == - 1 || str[j] == str[k])
		{
			++k;
			++j;
			next[j] = k; //没有优化过的
			// 优化
			/*if (str[k] != str[j])
			{
				next[j] = k;
			}
			else
			{
				next[j] = next[k];
			}*/
		}
		else
		{
			k = next[k];
		}
	}
}

int main()
{
	while (~scanf("%s", str))
	{
		int cnt = 0;
		int len_len = strlen(str);
		str[len_len++] = '*';
		str[len_len] = '\0';
		int len = len_len;
		get_next();
		while(1)
		{
			if (next[len_len - 1] > 0)
			{
				ans[++cnt] = next[len_len - 1];
				// for (int i = 0; i < next[len_len - 1]; ++i)
				// {
					// printf("%c", str[i]);
				// }
				// printf("\n");
				len_len = next[len_len - 1] + 1;
				continue;
			}
			break;
		}
		for (int i = cnt; i >= 1; --i)
		{
			printf("%d ", ans[i]);
		}
		printf("%d\n", len - 1);
	}
	return 0;
}