Merge pull request div-bargali#539 from muskanlalit18/main

Add Sort 0 1 2 Technique

Author: div-bargali

C++/Data-Structures/Array/sort012.cpp

@@ -0,0 +1,79 @@
+//Demonstration of the Sort 0 1 2 Technique using 3 pointers.
+//index 0 - (low - 1) represent all the 0s
+//index low - (mid - 1) represent all the 1s
+//index high - (n-1) represent all the 2s
+//Example:
+// Initially: 0 1 2 1 2 0 1
+// Finally:
+// 0 0 1 1 1 1 2 2
+// | |
+// | |
+// low mid & high
+
+//Test cases:
+/*
+3
+5
+1 0 0 1 2
+0 0 1 1 2
+8
+0 0 1 0 1 2 2 1
+0 0 0 1 1 1 2 2
+3
+0 1 0
+0 0 1
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+
+void swap(int* a, int* b)
+ {
+ int temp = *a;
+ *a = *b;
+ *b = temp;
+}
+
+int main()
+ {
+ int test_cases;
+ cin>>test_cases;
+ while(test_cases--)
+ {
+ int n;
+ cin>>n;
+ int arr[n];
+ for(int i = 0; i<n; i++)
+ {
+ cin>>arr[i];
+ }
+ int low = 0, mid = 0, high = n-1;
+
+ //We use the mid pointer to traverse through the array
+ while(mid<=high)
+ {
+ if(arr[mid]==0)
+ {
+ swap(arr[mid++], arr[low++]);
+
+ }
+ else if(arr[mid]==1)
+ {
+ mid++;
+ }
+ else if(arr[mid]==2)
+ {
+ swap(arr[mid], arr[high]);
+ high--;
+ }
+ }
+
+ for(int i = 0; i<n; i++)
+ {
+ cout<<arr[i]<<" ";
+ }
+ cout<<endl;
+ }
+
+ return 0;
+ }