Answer :
Explanation :

1. Have two indexes pointing to two ends of array, say i and j. 2. Approach towards each other with a check condition that they dont cross each other. 3. Each iteration of while loop, swap the numbers pointed by two indexes when num[i] index number is not equal to 1.   void sort() {      int a[]={1,0,0,0,1,1,0,1,0,1,0,0,1,0};      int i=0;      int j=13;      int temp;       while(j>i)      {           if(a[i]==1)                  i++;           if(a[j]==0)                  j--;           if(a[i]==0)          {                  temp=a[i];                 a[i]=a[j];                 a[j]=temp;          }      }       for(i=0;i<14;i++)              Console.Write(a[i]+", "); } Output: 1,1,1,1,1,1,0,0,0,0,0,0,0