Merge pull request #575 from S-ahil-Saxen-a/custom

#573 Added Dutch National Flag Algo for arrays in C++

Arrays/dutchNationalFlag.cpp

@@ -0,0 +1,64 @@
+// GFG Question: https://practice.geeksforgeeks.org/problems/sort-an-array-of-0s-1s-and-2s4231/1
+// Sort an array of 0's, 1's and 2's
+
+
+/* Dutch National Flag Algorithm: 
+-----------------------------------
+Take three-pointers, namely - low, mid, high.
+We use low and mid pointers at the start, and the high pointer will point at the end of the given array.
+*/
+
+#include<bits/stdc++.h>
+using namespace std;
+
+class Solution
+{
+    public:
+    void sort012(int a[], int n)
+    {
+        // code here 
+
+        int low = 0, mid = 0, high = n-1;
+
+        while(high >= mid){
+
+            switch(a[mid]){
+
+                case 0:
+                    swap(a[low], a[mid]);
+                    low++;
+                    mid++;
+                    break;
+
+                case 1:
+                    mid++;
+                    break;
+
+                case 2:
+                    swap(a[mid], a[high]);
+                    high--;
+                    break;
+            }
+        }
+    }
+
+};
+
+int main() {
+     int t;
+     cin >> t;
+    while(t--){
+        int n;
+        cin >>n;
+        int a[n];
+        for (int i=0;i<n;i++){
+            cin >> a[i];
+        }
+        Solution ob;
+        ob. sort012(a, n);
+        for(int i=0; i<n; i++){
+            cout << a[i] <<"";
+        }
+        cout << endl;
+    return 0;
+}