运行/编译的时候总会现警报：>C:\Users\sz\source\repos\Project18\Project18\源.cpp(26,11): warning C4244: “=”: 从“_Ty”转换到“int”，可能丢失数据，有神马问题？
#include<iostream>
#include<string>
#include <algorithm>
#include <vector>
#include <memory>
#include<windows.h>
using namespace std;
void da()
{
    int n, max, b = 0, l = 1;
    cout << "有几个数";
    cin >> n;
    if (n < 2)
    {
        cout << "请尊重程序员，谢谢" << endl;
        system("pause");
        system("cls");
   
    }
    vector<double> a(n);
    for (b = 0; b < n; b++)
    {
        cout << "请输入第" << b + 1 << "个数";
        cin >> a[b];
    }
    max = a[0];
    for (b = 1; b < n; b++)
    {
        if (a[b] > max)
        {
            max = a[b];
            l = b;
        }
    }
    cout << "最"; Sleep(500); cout << "大"; Sleep(500); cout << "的"; Sleep(500); cout << "数"; Sleep(500); cout << "是"; Sleep(500); cout << max; Sleep(500); cout << "是"; Sleep(500); cout << "第"; Sleep(500); cout << ++l; Sleep(500); cout << "个"; Sleep(500);
    while (true)
    {
        NULL;
    }

}
void xiao()
{
    int n, min, b = 0, l = 2;
    cout << "有几个数";
    cin >> n;
    if (n < 2)
    {
        cout << "请尊重程序员，谢谢" << endl;
        system("pause");
        system("cls");

    }
    vector<double> a(n);
    for (b = 0; b < n; b++)
    {
        cout << "请输入第" << b + 1 << "个数";
        cin >> a[b];
    }
min = a[0];
    for (b = 1; b < n; b++)
    {
        if (a[b] < min)
        {
            min = a[b];
            l = b;
        }
    }
    cout << "最"; Sleep(500); cout << "小"; Sleep(500); cout << "的"; Sleep(500); cout << "数"; Sleep(500); cout << "是"; Sleep(500); cout << min;
    while (true)
    {
        NULL;
    }
}
int main()
{
    const double i = 1.2;
    cout << "正在加载中，请稍后。就一杯茶的功夫";
    Sleep(100000);
    cout << "求最大/小数，作者：万致远 版本" << i << endl;
    string da_xiao;
    cout << "求大？求小？";
    cin >> da_xiao;
    if (da_xiao=="大")
    {
        da();
    }
    else
    {
        if (da_xiao=="小")
        {
            xiao();
        }
        else
        {
            cout << "新功能正在开发中，或请更新版本";
        }
    }
}

[此贴子已经被作者于2020-4-9 09:56编辑过]

switch 后跟任何整型或枚举类型，或可按语境隐式转换到整型或枚举类型的类类型的表达式，或单个这种类型的非数组变量的，带花括号或等号初始化器的声明。

没有switch语句呀

哦，没仔细看，只看了个轮廓

等你把没必要的汉字删了再仔细看吧

估计就是说cpp文件不支持中文，可能丢失数据

string有可能存不下

#include<iostream>
#include<string>
#include <algorithm>
#include <vector>
#include <memory>

using namespace std;
void da()
{
    int n, max, b = 0, l = 1;
    cout << "有几个数";
    cin >> n;
    if (n < 2)
    {
        
        system("pause");
        system("cls");
   
    }
    vector<double> a(n);
    for (b = 0; b < n; b++)
    {
        cout << "请输入第" << b + 1 << "个数";
        cin >> a[b];
    }
    max = a[0];
    for (b = 1; b < n; b++)
    {
        if (a[b] > max)
        {
            max = a[b];
            l = b;
        }
    }
    
    while (true)
    {
        NULL;
    }

}
void xiao()
{
    int n, min, b = 0, l = 2;
    cout << "有几个数";
    cin >> n;
    if (n < 2)
    {
        
        system("pause");
        system("cls");

    }
    vector<double> a(n);
    for (b = 0; b < n; b++)
    {
        cout << "请输入第" << b + 1 << "个数";
        cin >> a[b];
    }
min = a[0];
    for (b = 1; b < n; b++)
    {
        if (a[b] < min)
        {
            min = a[b];
            l = b;
        }
    }
    
    while (true)
    {
        NULL;
    }
}
int main()
{
    string da_xiao;
    cout << "求大？求小？";
    cin >> da_xiao;
    if (da_xiao=="大")
    {
        da();
    }
    else
    {
        if (da_xiao=="小")
        {
            xiao();
        }
        else
        {
            cout << "新功能正在开发中，或请更新版本";
        }
    }
}

运行没问题，就是有点后怕

首先，这个警报跟强制类型转换有关，动态数组是double，而你多次将元素赋值给int型，所以会出现类型转换，转换后的结果可能与你实际结果不符。。。
你用的IDE应该是VS，我用VS2019，把所有的动态数组改成int型没有警报
但是我不知道你要的效果是不是这样，不一致再提出来，谢谢！