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Author: dingjikerbo

leetcode/solution/src/NextPermutation.java

@@ -8,26 +8,24 @@ public class NextPermutation {
      * 然后从升序中找到一个大于nums[i-1]的最小数与i-1交换，然后对升序整体revert为降序即可
      */
     public void nextPermutation(int[] nums) {
-        int i = nums.length - 1;
+        int i, j;
 
-        for ( ; i >= 0; i--) {
-            if (i > 0 && nums[i - 1] < nums[i]) {
+        for (i = nums.length - 1; i > 0; i--) {
+            if (nums[i - 1] < nums[i]) {
                 break;
             }
         }
 
-        if (i < 0) {
-            revert(nums, 0, nums.length - 1);
-            return;
-        }
-
-        for (int j = nums.length - 1; j >= i; j--) {
-            if (nums[j] > nums[i - 1]) {
-                swap(nums, j, i - 1);
-                revert(nums, i, nums.length - 1);
-                break;
+        if (i > 0) {
+            for (j = i; j < nums.length; j++) {
+                if (nums[j] <= nums[i - 1]) {
+                    break;
+                }
             }
+            swap(nums, i - 1, j - 1);
         }
+
+        revert(nums, i, nums.length - 1);
     }
 
     private void swap(int[] nums, int left, int right) {

leetcode/src/Main.java

@@ -2,6 +2,37 @@
 
 public class Main {
 
+    // 1 5 1
+    public void nextPermutation(int[] nums) {
+        int i = nums.length - 1, j;
+        for (i = nums.length - 1; i > 0; i--) {
+            if (nums[i - 1] < nums[i]) {
+                break;
+            }
+        }
+        if (i > 0) {
+            for (j = i; j < nums.length; j++) {
+                if (nums[j] <= nums[i - 1]) {
+                    break;
+                }
+            }
+            swap(nums, i - 1, j - 1);
+        }
+        revert(nums, i, nums.length - 1);
+    }
+
+    private void revert(int[] nums, int start, int end) {
+        for ( ; start < end; start++, end--) {
+            swap(nums, start, end);
+        }
+    }
+
+    private void swap(int[] nums, int i, int j) {
+        int t = nums[i];
+        nums[i] = nums[j];
+        nums[j] = t;
+    }
+
     public static void main(String[] args) {
     }
 }