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59 changes: 59 additions & 0 deletions Sort an array of 0s, 1s and 2s
Original file line number Diff line number Diff line change
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// C++ program to sort an array
// with 0, 1 and 2 in a single pass
#include <bits/stdc++.h>
using namespace std;

// Function to sort the input array,
// the array is assumed
// to have values in {0, 1, 2}
void sort012(int a[], int arr_size)
{
int lo = 0;
int hi = arr_size - 1;
int mid = 0;

// Iterate till all the elements
// are sorted
while (mid <= hi) {
switch (a[mid]) {

// If the element is 0
case 0:
swap(a[lo++], a[mid++]);
break;

// If the element is 1 .
case 1:
mid++;
break;

// If the element is 2
case 2:
swap(a[mid], a[hi--]);
break;
}
}
}

// Function to print array arr[]
void printArray(int arr[], int arr_size)
{
// Iterate and print every element
for (int i = 0; i < arr_size; i++)
cout << arr[i] << " ";
}

// Driver Code
int main()
{
int arr[] = { 0, 1, 1, 0, 1, 2, 1, 2, 0, 0, 0, 1 };
int n = sizeof(arr) / sizeof(arr[0]);

sort012(arr, n);

printArray(arr, n);

return 0;
}

// This code is contributed by Shivi_Aggarwal