subset

Author: yuzhangcmu

dfs/SubsetsWithDup.java

@@ -0,0 +1,38 @@
+package Algorithms.dfs;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class SubsetsWithDup {
+    public List<List<Integer>> subsetsWithDup(int[] num) {
+        List<List<Integer>> ret = new ArrayList<List<Integer>>();
+        
+        if (num == null) {
+            return ret;
+        }
+        
+        Arrays.sort(num);
+        
+        dfs(num, new ArrayList<Integer>(), ret, 0);
+        
+        return ret;
+    }
+    
+    public void dfs(int[] num, List<Integer> path, List<List<Integer>> ret, int index) {
+        ret.add(new ArrayList<Integer>(path));
+        
+        for (int i = index; i < num.length; i++) {
+            // skip the duplicate.
+            if (i > index && num[i] == num[i - 1]) {
+                continue;
+            }
+            
+            path.add(num[i]);
+            // 注意：这里是i + 1不是index + 1!!!
+            dfs(num, path, ret, i + 1);
+            path.remove(path.size() - 1);
+        }
+        
+    }
+}