Given a binary array, sort it using one traversal and no extra space.
Examples :
Input : 1 0 0 1 0 1 0 1 1 1 1 1 1 0 0 1 1 0 1 0 0 Output : 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 Explanation: The output is a sorted array of 0 and 1 Input : 1 0 1 0 1 0 1 0 Output : 0 0 0 0 1 1 1 1 Explanation: The output is a sorted array of 0 and 1
Approach: This concept is related to partition of quick sort . In quick sort’ partition, after one scan, the left of the array is smallest and right of the array is the largest of selected pivot element.
Algorithm:
- Create a variable index index = 0
- Traverse the array from start to end
- If the element is 0 then swap the current element with the element at index position and increment the index by 1.
- If the element is 1 keep the element as it is.
Implementation:
CPP
// CPP program to sort a binary array #include <iostream> using namespace std; void sortBinaryArray( int a[], int n) { int j = -1; for ( int i = 0; i < n; i++) { // if number is smaller than 1 // then swap it with j-th number if (a[i] < 1) { j++; swap(a[i], a[j]); } } } // Driver code int main() { int a[] = { 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0 }; int n = sizeof (a) / sizeof (a[0]); sortBinaryArray(a, n); for ( int i = 0; i < n; i++) cout << a[i] << " " ; return 0; } |
Java
// JAVA Code for Sort a binary // array using one traversal import java.util.*; class GFG { static void sortBinaryArray( int a[], int n) { int j = - 1 ; for ( int i = 0 ; i < n; i++) { // if number is smaller than 1 // then swap it with j-th number if (a[i] < 1 ) { j++; int temp = a[j]; a[j] = a[i]; a[i] = temp; } } } /* Driver program to test above function */ public static void main(String[] args) { int a[] = { 1 , 0 , 0 , 1 , 0 , 1 , 0 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 1 , 1 , 0 , 1 , 0 , 0 }; int n = a.length; sortBinaryArray(a, n); for ( int i = 0 ; i < n; i++) System.out.print(a[i] + " " ); } } |
Python3
# A Python program to sort a # binary array def sortBinaryArray(a, n): j = - 1 for i in range (n): # if number is smaller # than 1 then swap it # with j-th number if a[i] < 1 : j = j + 1 # swap a[i], a[j] = a[j], a[i] # Driver program a = [ 1 , 0 , 0 , 1 , 0 , 1 , 0 , 1 , 1 , 1 , 1 , 1 , 1 , 0 , 0 , 1 , 1 , 0 , 1 , 0 , 0 ] n = len (a) sortBinaryArray(a, n) for i in range (n): print (a[i], end = " " ) # This code is contributed by Shrikant13. |
C#
// C# Code for Sort a binary // array using one traversal using System; class GFG { static void sortBinaryArray( int [] a, int n) { int j = -1; for ( int i = 0; i < n; i++) { // if number is smaller than // 1 then swap it with j-th // number if (a[i] < 1) { j++; int temp = a[j]; a[j] = a[i]; a[i] = temp; } } } /* Driver program to test above function */ public static void Main() { int [] a = { 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0 }; int n = a.Length; sortBinaryArray(a, n); for ( int i = 0; i < n; i++) Console.Write(a[i] + " " ); } } // This code is contributed by vt_m. |
PHP
<?php // PHP Code for Sort a binary // array using one traversal function sortBinaryArray( $a , $n ) { $j = -1; for ( $i = 0; $i < $n ; $i ++) { // if number is smaller than // 1 then swap it with j-th // number if ( $a [ $i ] < 1) { $j ++; $temp = $a [ $j ]; $a [ $j ] = $a [ $i ]; $a [ $i ] = $temp ; } } for ( $i = 0; $i < $n ; $i ++) echo $a [ $i ] . " " ; } // Driver Code $a = array (1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0); $n = count ( $a ); sortBinaryArray( $a , $n ); // This code is contributed by Sam007 ?> |
Output :
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1
Complexity Analysis:
Only one traversal of the array is needed, So time Complexity is O(n).
The space required is constant.
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