PAT甲級真題 1077 Kuchiguse (20分) C++實現（倒序搜索字符串公共尾部）

題目

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

思路

建立字符串數組，用getline(cin, s[i])讀取含空格的整行字符串。(注意在這之前要用getchar()喫掉換行符)

以第一個字符串爲基準，從尾到頭檢查所有其它字符串尾部字符是否全部與其相同。若所有尾部都相同則記錄，然後檢查下一個尾部；若不同或有一個字符串到達了頭部則結束。

最後查看記錄的公共字符串，若爲空則輸出“nai”；不爲空則直接輸出。

字符串添加字符時 += 效率更高，因爲不需要重新建立對象，最後倒序輸出即可。

代碼

#include <iostream>
#include <vector>
using namespace std;

int main(){
    int n;
    cin >> n;
    getchar();  //吸收換行符
    vector<string> s(n);
    for (int i=0; i<n; i++){
        getline(cin, s[i]);
    }
    string common = "";

    int j = 1;
    while (1){
        bool flag = true;
        //取s[0]爲基準
        if (s[0].size() < j){
            break;
        }
        char ch = s[0][s[0].size()-j];
        //檢查剩下的s[1]…s[n-1]
        for (int i=0; i<n; i++){
            if (s[i].size()<j || s[i][s[i].size()-j]!=ch){
                flag = false;
                break;
            }
        }
        if (flag){
            common += ch;
            j++;
        }
        else{
            break;
        }
    }
    if (common.size()==0){
        cout << "nai";
    }
    else{
        for (int i=common.size()-1; i>=0; i--){
            cout << common[i];
        }
    }
    return 0;
}