Data update

Task/Dutch-national-flag-problem/Java/dutch-national-flag-problem-2.java

@@ -0,0 +1,79 @@
+// Dutch national flag problem
+
+public class Main {
+
+  enum Color {BLUE, WHITE, RED};
+
+  static final int N = 20;
+
+  static void printColorSeq(Color[] t) {
+    int n = t.length;
+    for (int i = 0; i < n; i++) {
+      switch (t[i]) {
+      case BLUE:
+        System.out.print("B");
+        break;
+      case WHITE:
+        System.out.print("W");
+        break;
+      case RED:
+        System.out.print("R");
+        break;
+      }
+    }
+    System.out.println();
+  }
+
+  static void swapElems(Color[] arr, int i, int j) {
+    Color temp = arr[i];
+    arr[i] = arr[j];
+    arr[j] = temp;
+  }
+
+  static void sortByColor(Color[] t) {
+    int b = 0, w = 0, r = t.length - 1;
+    while (w <= r) {
+      switch (t[w]) {
+      case WHITE:
+        w++;
+        break;
+      case BLUE:
+        swapElems(t, b, w);
+        b++;
+        w++;
+        break;
+      case RED:
+        swapElems(t, w, r);
+        r--;
+        break;
+      }
+    }
+  }
+
+  public static void main(String[] args) {
+    Color[] t = new Color[N];
+
+    // Set colors
+    for (int i = 0; i < N; i++) {
+      int ci = (int)(Math.random() * 3);
+      switch (ci) {
+      case 0:
+        t[i] = Color.BLUE;
+        break;
+      case 1:
+        t[i] = Color.WHITE;
+        break;
+      case 2:
+        t[i] = Color.RED;
+        break;
+      }
+    }
+
+    System.out.println("Unsorted:");
+    printColorSeq(t);
+    sortByColor(t);
+    System.out.println();
+    System.out.println("Sorted:");
+    printColorSeq(t);
+  }
+}