conbinationsum

Author: zgpeace

code/LeetCode/src/backtracking/CombinationSum.java

@@ -0,0 +1,37 @@
+package backtracking;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+// https://leetcode.com/problems/combination-sum/
+public class CombinationSum {
+
+  public static void main(String[] args) {
+    CombinationSum obj = new CombinationSum();
+    int[] candicates = {2, 3, 6, 7};
+    int target = 7;
+    List<List<Integer>> resultList = obj.combinationSum(candicates, target);
+    System.out.println(Arrays.toString(resultList.toArray()));
+  }
+
+  public List<List<Integer>> combinationSum(int[] candidates, int target) {
+    List<List<Integer>> resultList = new ArrayList<>();
+    Arrays.sort(candidates);
+    recursive(candidates, target, 0, new ArrayList<>(), resultList);
+
+    return resultList;
+  }
+
+  public void recursive(int[] candidates, int target, int start, List<Integer> list, List<List<Integer>> resultList) {
+    if (target > 0) {
+      for (int i = start; i < candidates.length && target >= candidates[i]; i++) {
+        list.add(candidates[i]);
+        recursive(candidates, target - candidates[i], i, list, resultList);
+        list.remove(list.size() - 1);
+      }
+    } else if (target == 0) {
+      resultList.add(new ArrayList<>(list));
+    }
+  }
+}