尽管使用了标题#include <iostream>，Cout和Cin抛出错误

Question

编译下面的代码时出错 错误（有效）E0349无操作员“＆lt;＆lt;”或“＆gt;＆gt;”匹配这些操作数并强调cout＆lt;＆lt;和cin＆gt;＆gt;码。不确定是什么导致它。已包含标题#include。我将不胜感激任何帮助修复此错误或建议可能的原因。

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

void SSort(vector<string>& input) {
    int n = input.size();

    for (int i = 0; i < n - 1; i++) {

        int min_idx = i;
        for (int j = i + 1; j < n; j++)
            if (input[j] < input[min_idx])
                min_idx = j;

        string t = input[min_idx];
        input[min_idx] = input[i];
        input[i] = t;
    }
}


int BS(vector<string> input, string x) {

    int left = 0, right = input.size() - 1;
    while (left <= right) {
        int m = left + (right - left) / 2;


        if (input[m] == x)
            return m;

            if (input[m] < x)
            left = m + 1;


        else
            right = m - 1;
    }


    return -1;
}


void print(vector<string> input) {
    for (int i = 0; i < input.size(); i++)
        cout << input[i] << endl;
}


int main()
{
    vector<string> input;
    input.push_back("welcome");
    input.push_back("to");
    input.push_back("coding");
    input.push_back("test");
    input.push_back("selection");
    input.push_back("sort");
    input.push_back("using");
    input.push_back("binary");
    input.push_back("search");
    SSort(input);
    cout << "Sorted Vector: \n";
    print(input);
    while (true) {
        string key;
        cout << "Enter key to search: (press Q to exit)";
        cin >> key;
        if (key == "Q") {
            break;
        }
        int index = BS(input, key);

        if (index == -1)
            cout << key << " not in vector" << endl;
        else
            cout << key << " is at " << index << " in vector" << endl;
    }
    return 0;
}