c++ - 字符串 vector 输入和查询操作

Question

在我的 C++ 代码中，我获取了用户定义数量的输入字符串。接下来，用户输入用户定义数量的查询字符串。对于每个查询字符串，我想在用户最初输入的字符串集合中输出它的实例数。

这是我的代码:

#include<iostream>
#include<vector>
#include<string>
#include<conio.h>
using namespace std;
int main(int argc, char ** argv) {

    int N, Q;
    cout << "Enter number of strings : ";
    cin >> N;
    vector <string> strInp(N);
    string sbuf;

    // Storing the strings in the vector
    cout << "Enter the strings:" << endl;
    for (int i = 0; i < N; i++) {
        cin >> sbuf;
        strInp.push_back(sbuf);
    }

    // Storing the queries
    cout << "Enter the number of queries : ";
    cin >> Q;

    vector <string> query(Q);
    string qbuf;
    cout<<" Enter the query strings"<< endl;
    for (int i = 0; i < Q; i++) {
        cin >> qbuf;
        query.push_back(qbuf);
    }

    // Counting the instances of the query strings
    // Initializing the instances vector
    vector <int> instances;

    string s1, s2;
    int flag = 0;   

    vector <string> ::iterator start1 = query.begin();
    vector <string> ::iterator end1 = query.end();

    vector <string> ::iterator start2 = strInp.begin();
    vector <string> ::iterator end2 = strInp.end();

    for (auto i = start1; i < end1; i++) {
    int count = 0;
    s1 = *i;
    for (auto j = start2; j < end2; j++) {
        s2 = *j;
        if (s1 == s2) {
            count++;
        }           
    }
    instances.push_back(count);
    }

    cout << "The number of instances of each query are : " << endl;
    for (unsigned int i = 0; i < instances.size(); i++) {
        cout << instances[i] << endl;
    }



    return 0;
    _getch();
}

在运行代码时，我有以下输出

Enter the number of inputs : 5
Enter the strings:
apple
apple
apple
ball
cat

Enter the number of queries: 3
Enter the query strings:
apple
ball
cat

The number of instances of each query are :
5
5
5
3
1
1

预期的输出实际上是:

The number of instances of each query are :
3
1
1

如果有人能指出我做错了什么，我将不胜感激？谢谢你

Answer 1

当您创建 std::vector 时使用需要计数的构造函数，那么您已经填充了该数量的元素。

因此对于您的示例，这意味着 strInp是{"","","","","","apple","apple","apple","ball","cat"}和 query是{"","","","apple","ball","cat"}

因此您需要写入这些元素或创建一个空 vector 并使用 push_back。

原来如此 vector <string> strInp(N);和 vector <string> query(Q);和 strInp[i]=sbuf;和 query[i]=qbuf;

或者是

vector <string> strInp;和 vector <string> query;和 strInp.push_back(sbuf);和 query.push_back(qbuf);