Coursera - algorithms part 1 - integer array permutations

coursera/algorithms-part1/elementary-sorts/Permutation.java

@@ -0,0 +1,48 @@
+/**
+ * Coursera - Algorithms Part I
+ * Week 2 - Interview Questions - Elementary Sorts
+ *
+ * Question 2: Permutation
+ * Given two integer arrays of size N, design a subquadratic algorithm to
+ * determine whether one is a permutation of the other. That is, do they
+ * contain exactly the same entries but, possibly, in a different order.
+ *
+ * Solution:
+ *
+ * Sort each integer array and run a linear comparison. If any integer does
+ * not align with the other array, then they are not a permutation of each
+ * other.
+ */
+
+import java.util.Arrays;
+
+class Permutation {
+
+  private static boolean isPermutation(int[] a, int[] b) {
+    int[] a1 = new int[a.length];
+    int[] b1 = new int[b.length];
+    System.arraycopy(a, 0, a1, 0, a.length);
+    System.arraycopy(b, 0, b1, 0, b.length);
+
+    Arrays.sort(a1);
+    Arrays.sort(b1);
+
+    for (int i = 0; i < a1.length; ++i) {
+      if (a1[i] != b1[i]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  public static void main(String[] args) {
+    int[] a = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+    int[] b = { 1, 3, 4, 6 };
+    int[] c = { 1, 3, 5, 7, 9, 2, 4, 6, 8 };
+    System.out.println(isPermutation(a, b));
+    System.out.println(isPermutation(a, c));
+    System.out.println(isPermutation(a, a));
+    System.out.println(isPermutation(b, c));
+  }
+}