5.11 Next Perm - Add initial attempt (swap & sort)

Author: linton2000

epi_judge_java/epi/NextPermutation.java

@@ -2,12 +2,29 @@
 import epi.test_framework.EpiTest;
 import epi.test_framework.GenericTest;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
+
 public class NextPermutation {
   @EpiTest(testDataFile = "next_permutation.tsv")
   public static List<Integer> nextPermutation(List<Integer> perm) {
-    // TODO - you fill in here.
-    return null;
+    // Initial Attempt - Swapping & sorting to get next perm
+    // Time: O(nlogn), Space: O(1)
+    for (int i = perm.size() - 1; i > 0; i--) {
+      if (perm.get(i-1) < perm.get(i)) {
+        int di = i - 1;   // Index of 1st non-conforming (decreasing) digit from the right
+        int dk = i;       // Index of smallest element bigger & to the right of perm[di]
+        for (int j = i; j < perm.size(); j++) {
+          if (perm.get(j) > perm.get(di) && perm.get(j) < perm.get(dk))
+            dk = j;
+        }
+        Collections.swap(perm, di, dk);
+        Collections.sort(perm.subList(di + 1, perm.size()));  // Sort all elements after perm[di]
+        return perm;
+      }
+    }
+    return new ArrayList<>();
   }
 
   public static void main(String[] args) {

problem_mapping.js

@@ -330,7 +330,7 @@ problem_mapping = {
                 "total": 2001
             },
             "Java: NextPermutation.java": {
-                "passed": 0,
+                "passed": 2001,
                 "total": 2001
             },
             "Python: next_permutation.py": {