PAT 甲级 A1077 （2019/02/19）

#include<cstdio>
#include<cstring>
int n, minlen = 256, cnt = 0;
char str[100][256];
int main(){
    scanf("%d", &n);
    getchar();  //接收换行符
    for(int i = 0; i < n; i++){
        fgets(str[i],256,stdin);
        int len = strlen(str[i])-1;
        if(len < minlen) minlen = len; 
        for(int j = 0; j < len/2; j++){
            char temp = str[i][j];
            str[i][j] = str[i][len-j-1];
            str[i][len-j-1] = temp;
        }
    }
    for(int i = 0; i < minlen; i++){
        char ch = str[0][i];
        bool same = true;
        for(int j = 1; j < n; j++){
            if(ch != str[j][i]){
                same = false;
                break;
            }
        }
        if(same)    cnt++; 
        else    break;
    }
    if(cnt != 0){
        for(int i = cnt - 1; i >= 0; i--){
            printf("%c",str[0][i]); 
        }   
    }   
    else{
        printf("nai");
    }
    return 0;
}