回溯法 开头 基础+排列

Author: h2pl

src/BackTracking/找出有重复数字的组合.java

@@ -0,0 +1,36 @@
+package BackTracking;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Created by 周杰伦 on 2018/4/1.
+ */
+public class 找出有重复数字的组合 {
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        List<List<Integer>> ret = new ArrayList<>();
+        List<Integer> permuteList = new ArrayList<>();
+        Arrays.sort(nums);
+        boolean[] visited = new boolean[nums.length];
+        backtracking(permuteList, visited, nums, ret);
+        return ret;
+    }
+
+    private void backtracking(List<Integer> permuteList, boolean[] visited, int[] nums, List<List<Integer>> ret) {
+        if (permuteList.size() == nums.length) {
+            ret.add(new ArrayList(permuteList));
+            return;
+        }
+
+        for (int i = 0; i < visited.length; i++) {
+            if (i != 0 && nums[i] == nums[i - 1] && !visited[i - 1]) continue;
+            if (visited[i]) continue;
+            visited[i] = true;
+            permuteList.add(nums[i]);
+            backtracking(permuteList, visited, nums, ret);
+            permuteList.remove(permuteList.size() - 1);
+            visited[i] = false;
+        }
+    }
+}