POJ2159 Ancient Cipher

2159:Ancient Cipher

题目分析：很简单的一道题。大意是判断两个字符序列是否可以通过字符替换（substitution ）和交换（permutation）变成对方。初看似乎需要穷举所有substitution和permutation序列，但细想后发现：

1.permutation让序列不用考虑顺序问题，可以看作是两个字符集合，题目简化为判断两个字符集合是否可通过substitution得到。

2.substitution是任意的，只要两个序列中两个字符出现的次数相同，就可以替换。如果整个集合A中的字符都能在集合B中找到出现次数相同的字符，则A和B可以通过substitution得到。更进一步，只要统计集合A和集合B中出现次数为p(p>=1)的不同字符数目是否相等即可。

代码：

#include <stdio.h>
#include <string.h>
int main(){
	char encryted[105];
	char original[105];
	int mapEN[26],mapOR[26];
	memset(mapEN,0,sizeof(mapEN));
	memset(mapOR,0,sizeof(mapOR));

	scanf("%s%s",encryted,original);
	for(int i=0; encryted[i] != '\0'; i++){
		mapEN[encryted[i]-'A']++;
		mapOR[original[i]-'A']++;
	}

	int charCount[105];
	memset(charCount,0,sizeof(charCount));
	for(int i = 0; i<26; i++){
		charCount[mapEN[i]]++;
		charCount[mapOR[i]]--;
	}

	bool flag = true;
	for(int i = 0; i < 105; i++){
		if(charCount[i] != 0){
			flag = false;
			break;
		}
	}

	if(flag == true)
		printf("YES\n");
	else
		printf("NO\n");
	return 0;
}

题目：

时间限制: 1000ms 内存限制: 65536kB
描述
Ancient Roman empire had a strong government system with various departments, including a secret service department. Important documents were sent between provinces and the capital in encrypted form to prevent eavesdropping. The most popular ciphers in those times were so called substitution cipher and permutation cipher.
Substitution cipher changes all occurrences of each letter to some other letter. Substitutes for all letters must be different. For some letters substitute letter may coincide with the original letter. For example, applying substitution cipher that changes all letters from 'A' to 'Y' to the next ones in the alphabet, and changes 'Z' to 'A', to the message "VICTORIOUS" one gets the message "WJDUPSJPVT".
Permutation cipher applies some permutation to the letters of the message. For example, applying the permutation <2, 1, 5, 4, 3, 7, 6, 10, 9, 8> to the message "VICTORIOUS" one gets the message "IVOTCIRSUO".
It was quickly noticed that being applied separately, both substitution cipher and permutation cipher were rather weak. But when being combined, they were strong enough for those times. Thus, the most important messages were first encrypted using substitution cipher, and then the result was encrypted using permutation cipher. Encrypting the message "VICTORIOUS" with the combination of the ciphers described above one gets the message "JWPUDJSTVP".
Archeologists have recently found the message engraved on a stone plate. At the first glance it seemed completely meaningless, so it was suggested that the message was encrypted with some substitution and permutation ciphers. They have conjectured the possible text of the original message that was encrypted, and now they want to check their conjecture. They need a computer program to do it, so you have to write one.
输入
Input contains two lines. The first line contains the message engraved on the plate. Before encrypting, all spaces and punctuation marks were removed, so the encrypted message contains only capital letters of the English alphabet. The second line contains the original message that is conjectured to be encrypted in the message on the first line. It also contains only capital letters of the English alphabet.
The lengths of both lines of the input are equal and do not exceed 100.
输出
Output "YES" if the message on the first line of the input file could be the result of encrypting the message on the second line, or "NO" in the other case.
样例输入
JWPUDJSTVP
VICTORIOUS
样例输出
YES