标签：扩展kmp

Clairewd’s message

2
abcdefghijklmnopqrstuvwxyz
abcdab
qwertyuiopasdfghjklzxcvbnm
qwertabcde

abcdabcd
qwertabcde

题意好难理解啊

先给你个table,也就是明文对应的暗文

再给你一个串, 里面是暗文+明文,明文不一定完整,甚至没有

让你以最短的形式补全这个串,前半部分为暗文,后半部分为对应的明文

先把串的明文找出来,以此为模式串,原串为主串,进行扩展kmp,然后遍历,发现i + extend[i]  >= len 的话就找到答案了,如果找不到就输出主串和模式串

/*************************************************************************
    > File Name: hdu4300.cpp
    > Author: ALex
    > Mail: zchao1995@gmail.com 
    > Created Time: 2015年01月30日 星期五 21时09分35秒
 ************************************************************************/

#include <map>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

const double pi = acos(-1);
const int inf = 0x3f3f3f3f;
const double eps = 1e-15;
typedef long long LL;
typedef pair <int, int> PLL;
const int N = 100010;
char T[N];
char S[N];
int next[N];
int extend[N];
char table[30];
char rtable[30];

void EXTEND_KMP ()
{
	int lens = strlen (S);
	int lent = strlen (T);
	next[0] = lent;
	int i, j, p, L;
	j = 0;
	while (j + 1 < lent && T[j] == T[j + 1])
	{
		++j;
	}
	next[1] = j;
	int a = 1;
	for (i = 2; i < lent; ++i)
	{
		p = next[a] + a - 1;
		L = next[i - a];
		if (i + L < p + 1)
		{
			next[i] = L;
		}
		else
		{
			j = max(0, p - i + 1);
			while (i + j < lent && T[i + j] == T[j])
			{
				++j;
			}
			next[i] = j;
			a = i;
		}
	}
	j = 0;
	while (j < lens && S[j] == T[j])
	{
		++j;
	}
	extend[0] = j;
	a = 0;
	for (i = 1; i < lens; ++i)
	{
		p = extend[a] + a - 1;
		L = next[i - a];
		if (L + i < p + 1)
		{
			extend[i] = L;
		}
		else
		{
			j = max(0, p - i + 1);
			while (i + j < lens && j < lent && S[i + j] == T[j])
			{
				++j;
			}
			extend[i] = j;
			a = i;
		}
	}
}

int main ()
{
	int t;
	scanf("%d", &t);
	while (t--)
	{
		scanf("%s", table);
		scanf("%s", S);
		int len = strlen (S);
		for (int i = 0; i < 26; ++i)
		{
			rtable[table[i] - 'a'] = 'a' + i;
		}
		for (int i = 0; i < len; ++i)
		{
			T[i] = rtable[S[i] - 'a'];
		}
		T[len] = '\0';
		EXTEND_KMP ();
		bool flag = false;
		int e;
		int mid = len / 2 + (len % 2 ? 1 : 0);
		for (int i = 0; i < len; ++i)
		{
			if (extend[i] + i >= len && i >= mid)
			{
				e = i;
				flag = true;
				break;
			}
		}
		if (!flag)
		{
			printf("%s%s\n", S, T);
			continue;
		}
		for (int i = 0; i < e; ++i)
		{
			printf("%c", S[i]);
		}
		for (int i = 0; i < e; ++i)
		{
			printf("%c", T[i]);
		}
		printf("\n");
	}
	return 0;
}

hdu4300---Clairewd’s message

标签：扩展kmp

原文地址：http://blog.csdn.net/guard_mine/article/details/43316545