PAT 1077. Kuchiguse

The Japanese language is notorious for its sentence ending particles. Personal preference of such particles can be considered as a reflection of the speaker's personality. Such a preference is called "Kuchiguse" and is often exaggerated artistically in Anime and Manga. For example, the artificial sentence ending particle "nyan~" is often used as a stereotype for characters with a cat-like personality:

Itai nyan~ (It hurts, nyan~)
Ninjin wa iyada nyan~ (I hate carrots, nyan~)
Now given a few lines spoken by the same character, can you find her Kuchiguse?

Input Specification:

Each input file contains one test case. For each case, the first line is an integer N (2<=N<=100). Following are N file lines of 0~256 (inclusive) characters in length, each representing a character's spoken line. The spoken lines are case sensitive.

Output Specification:

For each test case, print in one line the kuchiguse of the character, i.e., the longest common suffix of all N lines. If there is no such suffix, write "nai".

Sample Input 1:

3
Itai nyan~
Ninjin wa iyadanyan~
uhhh nyan~

Sample Output 1:

nyan~

Sample Input 2:

3
Itai!
Ninjinnwaiyada T_T
T_T

Sample Output 2:

nai

分析

直接两两比较，从结尾开始往前找到公共部分，如果找到了公共部分就把它赋给s1，继续读入s2，重复前面的行为。如果没有公共部分了，flag=0，最后输出nai。

using namespace std;
int main(){
	int n,flag=1;
	cin>>n;
	getchar(); // 把换行符吃掉
	string s1,s2;
	getline(cin,s1);
	for(int i=1;i<n;i++){
		getline(cin,s2);
		if(flag==0) continue;
		int t1=s1.size()-1,t2=s2.size()-1;
		while(t1>=0&&t2>=0){
			if(s1[t1]==s2[t2]){
				t1--; t2--;
			}else{
				break;
			}
		}
		if(t1!=s1.size()-1) s1=s1.substr(t1+1);
		else flag=0;
	}
	if(flag==1) cout<<s1;
	else cout<<"nai";
	return 0;
}