为什么我的选择排序返回的值不在原始向量中？

Question

I've been tinkering around with it for a while now and I'm so close! Now the output seems to be continuously printing a zero as the first value of the "sorted" vector. This is homework on how to create a selection sort in C++.

Example Output

Vector: 6, 2, 11, 1, 12, 4

Sorted Vector: 0, 2, 11, 6, 12, 4

Code

void selectionSort (vector<int>& data)
{
    int min, temp, n=data.size(), i, j;

    for (i=0; i<n; i++)
    {
        min = i;
        for (j=i+1; j<n; j++)
        {   
            if (data[min]>data[j])
            {
                min=j;
            }   
            temp=data[min];
            data[min]=data[i];
            data[i]=temp;
        }
        return;
    }   
}

int main()
{
    int n;
    vector<int> data;

    cout<<"Vector length?: "<<endl;
    cin>>n;

    srand(time(0));
    for (int i=0; i<n; i++)
    {
        data.push_back(rand()%20+1);
    }

    cout<<"Vector: "<<endl;
    for (int i=0; i<n; i++)
    {
        cout<<data[i]<<" "<<endl;
    }

    selectionSort(data);

    cout<<"Selection Sorted Vector: "<<endl;
    for (int i=0; i<data.size(); i++)
    {
        cout<<data[i]<<" "<<endl;
    }

    system("Pause");

    return 0;




}

Answer 1

Given an array of n elements, a selection sort performs n swaps.

1. You're performing far more swaps than that.
2. You also have an unexpectedly early call to return .

Let's look at a proper implementation of the sort:

#include <iostream>
#include <vector>
using namespace std;

void selectionSort (vector<int>& data)
{
    const int n = data.size();

    for (int i=0; i<n; i++)
    {
        int min = i;
        for (int j=i+1; j<n; j++)
            if (data[min]>data[j])
                min = j;

        swap(data[min], data[i]);
    }
}

int main() {
    vector<int> data = {6, 2, 11, 1, 12, 4};
    selectionSort(data);

    for (auto element : data)
        cout << element << " ";
    cout << "\n";
}

Which outputs:

1 2 4 6 11 12 

Answer 2

Consider the following correct implementation of a selection sort and compare it to yours:

#include <iostream>
#include <vector>

void selection_sort(std::vector<int> &numbers)
{
    // Iterate through all possible start indices.
    for (int i = 0; i < numbers.size(); ++i)
    {
        // Determine the index of the minimum for this iteration.
        int index_of_min = i;
        for (int j = i; j < numbers.size(); ++j)
        {
            if (numbers[j] < numbers[index_of_min])
            {
                index_of_min = j;
            }
        }
        // Swap the minimum element with the element at the start index.
        int temp = numbers[i];
        numbers[i] = numbers[index_of_min];
        numbers[index_of_min] = temp;
    }
}

int main()
{
    std::vector<int> numbers = { 20, 17, 13, 12, 25 };

    selection_sort(numbers);

    for (size_t i = 0; i < numbers.size(); ++i)
    {
        std::cout << numbers[i] << " ";
    }
}