Question

我有这样的东西：

<?php
echo exec('"C:\Program Files (x86)\Microsoft Visual Studio\VB98\VB6.EXE" /MAKE D:\Websites\devopservices\dlledit\portaleeditorisen\NewSecurity\Data\NewSecurity_Data.vbp D:\Websites\devopservices\dlledit\compiled\NewSecurity_Data.dll');
?>

现在，我没有在#include <iostream> #include <bits/stdc++.h> using namespace std; void shortestRemainingTime(map<string, string> processes[]){ int size = (sizeof(processes)/sizeof(*processes)); cout << size; } int main() { map<string, string> process { { "name", "open paint" }, { "remainingTime", "1000" } }; map<string, string> process2{ { "name", "open photoshop" }, { "remainingTime", "500" } }; map<string, string> process3{ { "name", "open word" }, { "remainingTime", "600" } }; map<string, string> processes[] = {process, process2, process3}; shortestRemainingTime(processes); return 0; }中进行任何计算，但是，当我打印地图shortestRemainingTime的数组大小时，我得到0，这是不对的。

如何获得这个特殊数组的正确长度？

processes

Answer 1

当将数组作为参数传递给函数时，它decays into a pointer，因此，您不能在其上使用sizeof(processes)/sizeof(*processes)范式/方法。

>

您应该使用std::vector代替数组，在这种情况下，您可以使用其size()函数。这是执行此操作的代码版本：

#include <iostream>
#include <map>
#include <vector>
#include <string>
using std::cout;
using std::vector;
using std::map;
using std::string;

// Note: Passing the vector by reference avoids having to copy a (potentially) 
// large object. Remove the "const" qualifier if you want the function to modify
// anything in the vector...
void shortestRemainingTime(const vector<map<string, string>> &processes)
{
    size_t size = processes.size();
    cout << size;
}

int main()
{
    map<string, string> process{ { "name", "open paint" }, { "remainingTime", "1000" } };
    map<string, string> process2{ { "name", "open photoshop" }, { "remainingTime", "500" } };
    map<string, string> process3{ { "name", "open word" }, { "remainingTime", "600" } };

    vector<map<string, string>> processes = { process, process2, process3 };
    shortestRemainingTime(processes);
    return 0;
}

此外，请参见以下内容：Why should I not #include <bits/stdc++.h>?和Why is "using namespace std;" considered bad practice?，以获取良好的编码准则。

获取地图数组的长度

1 个答案: