solve 40.combination-sum-ii

Author: andavid

vscode/40.combination-sum-ii.java

@@ -0,0 +1,76 @@
+/*
+ * @lc app=leetcode id=40 lang=java
+ *
+ * [40] Combination Sum II
+ *
+ * https://leetcode.com/problems/combination-sum-ii/description/
+ *
+ * algorithms
+ * Medium (43.08%)
+ * Likes:    1009
+ * Dislikes: 50
+ * Total Accepted:    244.2K
+ * Total Submissions: 566.1K
+ * Testcase Example:  '[10,1,2,7,6,1,5]\n8'
+ *
+ * Given a collection of candidate numbers (candidates) and a target number
+ * (target), find all unique combinations in candidates where the candidate
+ * numbers sums to target.
+ *
+ * Each number in candidates may only be used once in the combination.
+ *
+ * Note:
+ *
+ *
+ * All numbers (including target) will be positive integers.
+ * The solution set must not contain duplicate combinations.
+ *
+ *
+ * Example 1:
+ *
+ *
+ * Input: candidates = [10,1,2,7,6,1,5], target = 8,
+ * A solution set is:
+ * [
+ * ⁠ [1, 7],
+ * ⁠ [1, 2, 5],
+ * ⁠ [2, 6],
+ * ⁠ [1, 1, 6]
+ * ]
+ *
+ *
+ * Example 2:
+ *
+ *
+ * Input: candidates = [2,5,2,1,2], target = 5,
+ * A solution set is:
+ * [
+ * [1,2,2],
+ * [5]
+ * ]
+ *
+ *
+ */
+class Solution {
+  public List<List<Integer>> combinationSum2(int[] candidates, int target) {
+    List<List<Integer>> list = new ArrayList<>();
+    Arrays.sort(candidates);
+    backtrack(list, new ArrayList<>(), candidates, target, 0);
+    return list;
+  }
+
+  public void backtrack(List<List<Integer>> list, List<Integer> track, int[] candidates, int remain, int start) {
+    if (remain < 0) return;
+    if (remain == 0) {
+      list.add(new ArrayList<>(track));
+    } else {
+      for (int i = start; i < candidates.length; i++) {
+        if (i > start && candidates[i] == candidates[i - 1]) continue;
+        track.add(candidates[i]);
+        backtrack(list, track, candidates, remain - candidates[i], i + 1);
+        track.remove(track.size() - 1);
+      }
+    }
+  }
+}
+