c++ - 数组的前一行元素也得到更新

Question

in this program i am separating integers from a character array which consists of a space between them

#include<iostream>     
#include<stdio.h>     
#include<conio.h>
using namespace std;
int main()
{
    int i = 0, t, l = 0, j, c, k, q = 0, num = 0;
    char ch[10][10];
    int ach[10][1];
    cout << "enter the number of test cases";
    cin >> t;
    for (i = 0; i < t; i++)
    {
        fflush(stdin);
        cin.getline(ch[i], 9);
    }

    for (i = 0; i < t; i++)
    {
        num = 0;

        for (j = 0; ch[i][j] != '\0'; j++) //calculating length   
        {
            l = j;
        }
        l = l + 1;

        for (j = 0; j < l; j++)
        {
            if (ch[i][j] == ' ') //finding the space     
                c = j;
        }

        for (k = 0; k < c; k++) //taking first integer out of char array    
        {
            q = ch[i][k] - 48;    //parsing char to int
            num = (num * 10) + q;
        }
        cout << "\n previous row element " << ach[0][1] << "\n"; //checking the value    

        ach[i][0] = num; // this statement is updating the previous row's last element of the array    

        cout << "\n previous row element " << ach[0][1] << "\n"; //checking the value    
        cout << ach[i][0];

        num = 0;
        q = 0;
        for (k = c + 1; k < l; k++) //taking second element out of char array     
        {
            q = ch[i][k] - 48;     //parsing char to int
            num = (num * 10) + q;
        }

        ach[i][1] = num;
        cout << ach[i][1];
    }

    for (i = 0; i < t; i++)
    {
        cout << "\n" << ach[i][0] << "\t" << ach[i][1] << "\n"; //displaying the values       
    }

    getch();
    return 0;
}

I have marked the code that is malfunctioning , it is updating the previous row's last element. please help.

Answer 1

哎呀，你的代码没有真正优化，主要是 C，除了 cin.getline。但您真正的问题是，对于 int ach[10][1]，ach 是一个大小为 10x1 的二维数组，因此 ach[i][1] 可能不是您所期望的，因为您应该定义 int ach[10][2] 以安全地使用它。数组索引计算规则给出 &(ach[i][1]) == &ach[0][0] + i*1 + 1 所以你实际上访问的是 ach[i +1][0] 如果 i 为 9，则可能有一个尾端数组访问。

此外，在第一次访问时，ach[0][1] 没有首先被初始化就被使用。

所以你的 ach 定义应该是:

int ach[10][2] = {0};