Selection Sort — Algorithm Animation

What does it solve?

Sorts an array by dividing it into a sorted region (left) and an unsorted region (right). On each pass it scans the unsorted region to find the minimum element.

That minimum is then swapped into the front of the unsorted region, growing the sorted region by one element each pass — until the whole array is sorted.

The core idea

// for each boundary position i:
minIdx = i
for j = i+1 to n-1:
if arr[j] < arr[minIdx]:
minIdx = j
swap(arr[i], arr[minIdx])

Complexity

Time complexity

O(N²)

Always scans the remaining unsorted region for each of the N positions — same in best, average, and worst case.

Space complexity

O(1)

Sorts in place — only a few index variables are needed beyond the input array.

Examples & edge cases

Live animation

Comparing (j) Current minimum Boundary (i) Sorted

Step — of —

Boundary (i)

—

Comparing (j)

—

Current min

—

at index —

Swaps so far

—

total

Select an example and press Play to start.

✓ Sorted

Speed Medium

Step-by-step table

Step	i	j	Action	Array state	Note

C++ implementation

selection_sort.cpp

#include <bits/stdc++.h>
using namespace std;

void selectionSort(vector<int>& arr) {
    int n = arr.size();
    for (int i = 0; i < n - 1; i++) {
        int minIdx = i;
        for (int j = i + 1; j < n; j++) {
            if (arr[j] < arr[minIdx]) {
                minIdx = j;              // found a new minimum
            }
        }
        if (minIdx != i) {
            swap(arr[i], arr[minIdx]);   // place min at boundary
        }
    }
}

int main() {
    vector<int> arr = {29, 10, 14, 37, 13};
    selectionSort(arr);

    for (int x : arr) cout << x << " ";
    cout << "\n";
    return 0;
}

My Notes

📝 Notes ✅

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