冒泡排序的 C++ 问题

Question

I am attempting to use bubble sort in C++ which I am new to. This is my code so far:

My issue is that when ever I try and sort the arrays, the integer array is set to zero at every index.

Could this have something to do with memory allocation?

#include <iostream>
#include <cstring>
#include <array>

using namespace std;

int main() {
    //requires users input to create an array that wouldn't use too much memory
    cout << "Enter number of dealers you wish to enter" << endl;
    int array_size;
    cin >> array_size;
    std::string sales_names[array_size]; //makes a 2D array that can have 15 rows and 2 colums {Name, sales total}
    int sales_data[array_size];

    for(int i = 0; i < array_size; i++){
        std::string dealers_name;
        int dealers_value;
        cout << "Enter Dealers Name: ";
        cin >> dealers_name;
        cin.clear();
        cout << "Enter Dealers Sales: ";
        cin >> dealers_value;
        sales_names[i] = dealers_name;
        sales_data[i] = dealers_value;
        cout << endl;
    }

    string temp_name;
    int temp_value;

    //Bubble Sort?
    for(int i = 0; i < array_size; i++){
        for(int k = 0; k < array_size; k++){
            if(sales_data[k] = sales_data[k+1])
            {
                temp_value = sales_data[k];
                temp_name = sales_names[k];

                sales_data[k] = sales_data[k+1];
                sales_names[k] = sales_names[k+1];

                sales_data[k+1] = temp_value;
                sales_names[k+1] = temp_name;
            }
        }
    }

    for(int i = 0; i < array_size; i++){
        cout << sales_data[i] << endl;
        cout << sales_names[i] << endl;
    }

    return 0;
}

Im not sure why, but after the first loop of the for loop, every item in the sales_data array is set to 0

Here is my output:

Enter number of dealers you wish to enter
3
Enter Dealers Name:test1
 Enter Dealers Sales:12

Enter Dealers Name:test2
 Enter Dealers Sales:6

Enter Dealers Name:test3
 Enter Dealers Sales:9

0
test3
0
test2
0
test1

Thanks in advance

Answer 1

You have two obvious problems.

In

for(int i = 0; i < array_size; i++){
    for(int k = 0; k < array_size; k++){
        if(sales_data[k] = sales_data[k+1])

you are assigning ( = ) instead of comparing ( == ). Though there's no point in a bubble if they match. Perhaps you want less than?

Also, watch out for running up to k , and inspecting k+1

Answer 2

There are multiple issues with your code:

• sales_data[k] = sales_data[k+1] should be sales_data[k] == sales_data[k+1]

• for(int k = 0; k < array_size; k++) loop should start from i+1 for a bubble sort or you can change the condition to k < array_size-i-1

Answer 3

Your comparison is wrong:

if (sales_data[k] = sales_data[k + 1])

This should be a < (or a > , depending on if you want to sort ascending or descending). Even if you wanted to test for equality, == would have been right, not = . Also here

for (int k = 0; k < array_size-1; k++) {

You should put array_size-1 , otherwise it's going out of bounds.

Also note that VLAs aren't actually part of standard C++. Use std::vector instead:

std::vector<std::string> sales_names(array_size);
std::vector<int> sales_data(array_size);

By the way, that comment about it making a 2D array is wrong.

Answer 4

2 changes/questions:

1. Why are you swapping when data is same ? You only need to swap if i < k and arr[i] > arr[k].

2. You are going out of bounds when accessing k+1 for inner loop, it should be k

.