Added and edited Dtch_national_flag

Author: Shantanuu-eng

Dutch_national_flag2.java

@@ -0,0 +1,62 @@
+/*The problem was posed with three colours, here `0′, `1′ and `2′. The array is divided into four sections: 
+a[1..Lo-1] zeroes (red)
+a[Lo..Mid-1] ones (white)
+a[Mid..Hi] unknown
+a[Hi+1..N] twos (blue)
+If the ith element is 0 then swap the element to the low range, thus shrinking the unknown range.
+Similarly, if the element is 1 then keep it as it is but shrink the unknown range.
+If the element is 2 then swap it with an element in high range. */
+import java.io.*; 
+ 
+class countzot {
+ 
+    // Sort the input array, the array is assumed to
+    // have values in {0, 1, 2}
+    static void sort012(int a[], int arr_size)
+    {
+        int lo = 0;
+        int hi = arr_size - 1;
+        int mid = 0, temp = 0;
+        while (mid <= hi) {
+            switch (a[mid]) {
+            case 0: {
+                temp = a[lo];
+                a[lo] = a[mid];
+                a[mid] = temp;
+                lo++;
+                mid++;
+                break;
+            }
+            case 1:
+                mid++;
+                break;
+            case 2: {
+                temp = a[mid];
+                a[mid] = a[hi];
+                a[hi] = temp;
+                hi--;
+                break;
+            }
+            }
+        }
+    }
+ 
+    /* Utility function to print array arr[] */
+    static void printArray(int arr[], int arr_size)
+    {
+        int i;
+        for (i = 0; i < arr_size; i++)
+            System.out.print(arr[i] + " ");
+        System.out.println("");
+    }
+ 
+    /*Driver function to check for above functions*/
+    public static void main(String[] args)
+    {
+        int arr[] = { 0, 1, 1, 0, 1, 2, 1, 2, 0, 0, 0, 1 };
+        int arr_size = arr.length;
+        sort012(arr, arr_size);
+        System.out.println("Array after seggregation ");
+        printArray(arr, arr_size);
+    }
+}