c++ - 代码具有特定于功能的变量，这些变量在范围之外更改值

Question

这是FCFS cpu调度算法。

void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[])
{

// Calculating turnaround time by adding bt[i] + wt[i] 
    for (int i = 0; i < n; i++)
        tat[i] = bt[i] + wt[i];
}

// Function to calculate average waiting and turn-around 
// times. 
void findavgTime(int processes[], int n, int bt[], int at[])
{
    int wt[n], tat[n];

// Function to find waiting time of all processes 
    findWaitingTime(processes, n, bt, wt, at);

// Function to find turn around time for all processes 
    findTurnAroundTime(processes, n, bt, wt, tat);

// Display processes along with all details 
    cout << "Processes " << " Burst Time " << " Arrival Time "
            << " Waiting Time " << " Turn-Around Time "
            << " Completion Time \n";
    int total_wt = 0, total_tat = 0;
    for (int i = 0; i < n; i++)
    {
        total_wt = total_wt + wt[i];
        total_tat = total_tat + tat[i];
        int compl_time = tat[i] + at[i];
        cout << " " << i + 1 << "\t\t" << bt[i] << "\t\t" << at[i] << "\t\t"
                << wt[i] << "\t\t " << tat[i] << "\t\t " << compl_time << endl;
    }

    cout << "Average waiting time = " << (float) total_wt / (float) n;
    cout << "\nAverage turn around time = " << (float) total_tat / (float) n;
}

wt 和 tat 之类的变量如果在每个函数中都被清除，它们是如何连接的？(这是主要问题)

完整代码正在运行。

Answer 1

How are variables like wt and tat connected if they are decleared inside each function?

wt和 tat在 findavgTime 中定义. (它们是使用非标准扩展定义的，但这是一个单独的问题)。

当 findavgTime电话 findWaitingTime和 findTurnAroundTime ，它将这些变量传递给函数。这些函数不在函数体中定义它们——它们是通过函数参数在函数中定义的。自 wt和 tat是数组，当 findWaitingTime 时，它们衰减到指向相应数组第一个元素的指针和 findTurnAroundTime叫做。因此，对这些函数内的变量所做的任何更改都在 findavgTime 中可见。也是。

您不必在函数参数中使用相同的变量名。你可以使用

void findTurnAroundTime(int processes[], int n, int bt[], int wt_here[], int tat_here[])
{    
    for (int i = 0; i < n; i++)
        tat_here[i] = bt[i] + wt_here[i];
}

这不会改变程序的行为。