add a solution for 46

fishercoder1534 · fishercoder1534 · commit c6366ce46b08 · 2021-10-18T11:36:07.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_46.java b/src/main/java/com/fishercoder/solutions/_46.java
@@ -68,4 +68,33 @@ private void backtracking(List<Integer> list, int[] nums, Set<List<Integer>> ans
         }
     }
 
+    public static class Solution3 {
+        /**
+         * A more efficient version of backtracking.
+         */
+        public List<List<Integer>> permute(int[] nums) {
+            List<List<Integer>> ans = new ArrayList<>();
+            boolean[] used = new boolean[nums.length];
+            return backtracking(ans, used, new ArrayList<>(), nums);
+        }
+
+        private List<List<Integer>> backtracking(List<List<Integer>> ans, boolean[] used, List<Integer> list, int[] nums) {
+            if (list.size() == nums.length) {
+                ans.add(new ArrayList<>(list));
+                return ans;
+            }
+            for (int i = 0; i < nums.length; i++) {
+                if (used[i]) {
+                    continue;
+                }
+                used[i] = true;
+                list.add(nums[i]);
+                backtracking(ans, used, list, nums);
+                used[i] = false;
+                list.remove(list.size() - 1);
+            }
+            return ans;
+        }
+    }
+
 }
diff --git a/src/test/java/com/fishercoder/_46Test.java b/src/test/java/com/fishercoder/_46Test.java
@@ -8,22 +8,26 @@
 public class _46Test {
     private static _46.Solution1 solution1;
     private static _46.Solution2 solution2;
+    private static _46.Solution3 solution3;
 
     @BeforeClass
     public static void setup() {
         solution1 = new _46.Solution1();
         solution2 = new _46.Solution2();
+        solution3 = new _46.Solution3();
     }
 
     @Test
     public void test1() {
         CommonUtils.printListList(solution1.permute(new int[]{1, 2, 3}));
         CommonUtils.printListList(solution2.permute(new int[]{1, 2, 3}));
+        CommonUtils.printListList(solution3.permute(new int[]{1, 2, 3}));
     }
 
     @Test
     public void test2() {
         CommonUtils.printListList(solution1.permute(new int[]{1, 2, 3, 4, 5, 6}));
         CommonUtils.printListList(solution2.permute(new int[]{1, 2, 3, 4, 5, 6}));
+        CommonUtils.printListList(solution3.permute(new int[]{1, 2, 3, 4, 5, 6}));
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -8,22 +8,26 @@`
`8`	`8`	`public class _46Test {`
`9`	`9`	`private static _46.Solution1 solution1;`
`10`	`10`	`private static _46.Solution2 solution2;`
	`11`	`+ private static _46.Solution3 solution3;`
`11`	`12`
`12`	`13`	`@BeforeClass`
`13`	`14`	`public static void setup() {`
`14`	`15`	`solution1 = new _46.Solution1();`
`15`	`16`	`solution2 = new _46.Solution2();`
	`17`	`+ solution3 = new _46.Solution3();`
`16`	`18`	`}`
`17`	`19`
`18`	`20`	`@Test`
`19`	`21`	`public void test1() {`
`20`	`22`	`CommonUtils.printListList(solution1.permute(new int[]{1, 2, 3}));`
`21`	`23`	`CommonUtils.printListList(solution2.permute(new int[]{1, 2, 3}));`
	`24`	`+ CommonUtils.printListList(solution3.permute(new int[]{1, 2, 3}));`
`22`	`25`	`}`
`23`	`26`
`24`	`27`	`@Test`
`25`	`28`	`public void test2() {`
`26`	`29`	`CommonUtils.printListList(solution1.permute(new int[]{1, 2, 3, 4, 5, 6}));`
`27`	`30`	`CommonUtils.printListList(solution2.permute(new int[]{1, 2, 3, 4, 5, 6}));`
	`31`	`+ CommonUtils.printListList(solution3.permute(new int[]{1, 2, 3, 4, 5, 6}));`
`28`	`32`	`}`
`29`	`33`	`}`