40. Combination Sum II

Author: coderbean

src/leetcode/_40_/Main.java

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+package leetcode._40_;
+
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.combinationSum2(new int[]{10, 1, 2, 7, 6, 1, 5}, 10));
+    }
+}
+

src/leetcode/_40_/Solution.java

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+package leetcode._40_;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+class Solution {
+    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
+        Arrays.sort(candidates);
+        Set<List<Integer>> result = new HashSet<>();
+        for (int i = 0; i < candidates.length; i++) {
+            if (i > 1 && candidates[i] == candidates[i - 1]) {
+                continue;
+            }
+            if (target == candidates[i]) {
+                result.add(Collections.singletonList(target));
+            }
+            for (List<Integer> list : this.combinationSum2(candidates, i, target - candidates[i])) {
+                list.add(candidates[i]);
+                result.add(list);
+            }
+        }
+        return new ArrayList<>(result);
+    }
+
+    private List<List<Integer>> combinationSum2(int[] candidates, int index, int target) {
+        List<List<Integer>> result = new ArrayList<>();
+        if (target < candidates[index]) {
+            return result;
+        }
+        if (Arrays.binarySearch(candidates, index + 1, candidates.length, target) > 0) {
+            result.add(new ArrayList<>(Collections.singletonList(target)));
+        }
+        for (int i = index + 1; i < candidates.length; i++) {
+            for (List<Integer> list : this.combinationSum2(candidates, i, target - candidates[i])) {
+                list.add(candidates[i]);
+                result.add(list);
+            }
+        }
+        return result;
+    }
+}

src/leetcode/_40_/solution.md

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+### [40\. Combination Sum IICopy for MarkdownCopy for MarkdownCopy for Markdown](https://leetcode.com/problems/combination-sum-ii/)
+
+Difficulty: **Medium**
+
+
+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]
+]
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
+        Arrays.sort(candidates);
+        Set<List<Integer>> result = new HashSet<>();
+        for (int i = 0; i < candidates.length; i++) {
+            if (i > 1 && candidates[i] == candidates[i - 1]) {
+                continue;
+            }
+            if (target == candidates[i]) {
+                result.add(Collections.singletonList(target));
+            }
+            for (List<Integer> list : this.combinationSum2(candidates, i, target - candidates[i])) {
+                list.add(candidates[i]);
+                result.add(list);
+            }
+        }
+        return new ArrayList<>(result);
+    }
+​
+    private List<List<Integer>> combinationSum2(int[] candidates, int index, int target) {
+        List<List<Integer>> result = new ArrayList<>();
+        if (target < candidates[index]) {
+            return result;
+        }
+        if (Arrays.binarySearch(candidates, index + 1, candidates.length, target) > 0) {
+            result.add(new ArrayList<>(Collections.singletonList(target)));
+        }
+        for (int i = index + 1; i < candidates.length; i++) {
+            for (List<Integer> list : this.combinationSum2(candidates, i, target - candidates[i])) {
+                list.add(candidates[i]);
+                result.add(list);
+            }
+        }
+        return result;
+    }
+}
+            for (List<Integer> list : this.combinationSum2(candidates, i, target - candidates[i])) {
+```
+![](https://ws3.sinaimg.cn/large/006tKfTcgy1g1bpbuuppkj311a0q6tcn.jpg)