Question

How to sort an array of 0s, 1s and 2s in C++

Answer 1

#include <iostream>

void swap(int* a, int* b) {
    int tmp = *a;
    *a = *b;
    *b = tmp;
}

void sort012Array(int arr[], int size) {
    int lo = 0, curr = 0;
    int hi = size - 1;
    
    while (curr <= hi) {
        switch (arr[curr]) {
            case 0:
                swap(&arr[lo++], &arr[curr++]);
                break;
            case 1:
                curr++;
                break;
            case 2:
                swap(&arr[curr], &arr[hi--]);
                break;
        }
    }
}

int main()
{
    int arr[] = { 1, 2, 2, 0, 1, 1, 0, 2, 0, 1, 0, 0, 1 };

    int size = sizeof(arr) / sizeof(arr[0]);

    sort012Array(arr, size);

    for (int i = 0; i < size; i++)
        std::cout << arr[i] << " ";
}




/*
run:

0 0 0 0 0 1 1 1 1 1 2 2 2 

*/

 

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