Create 077. Combinations.java

Author: futurus

077. Combinations.java

@@ -0,0 +1,25 @@
+// https://leetcode.com/problems/combinations
+
+public class Solution {
+    public void helper(List<List<Integer>> result, ArrayList<Integer> current, int n, int k, int last) {
+        if (current.size() == k) {
+            result.add((ArrayList)current.clone());
+            return;
+        } else {
+            for (int i = last; i <= n; i++) {
+                current.add(i);
+                helper(result, current, n, k, i+1);
+                current.remove(current.indexOf(i));
+            }
+            return;
+        }
+    }
+    
+    public List<List<Integer>> combine(int n, int k) {
+        List<List<Integer>> result = new ArrayList<List<Integer>>();
+        
+        helper(result, new ArrayList<Integer>(), n, k, 1);
+        
+        return result;
+    }
+}