LeetCode | Combination Sum II

题目

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers
sums to T.

Each number in C may only be used once in the combination.

Note:

All numbers (including target) will be positive integers.
Elements in a combination (a1, a2,
… , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤
… ≤ ak).
The solution set must not contain duplicate combinations.

For example, given candidate set 

10,1,2,7,6,1,5

 and target 

8

, 

A solution set is: 

[1, 7]

 

[1, 2, 5]

 

[2, 6]

 

[1, 1, 6]

 
分析
和Combination Sum思路完全一致，注意去重即可。

代码

import java.util.ArrayList;
import java.util.Arrays;

public class CombinationSumII {
public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {
Arrays.sort(num);
ArrayList<ArrayList<Integer>> results = new ArrayList<ArrayList<Integer>>();
ArrayList<Integer> list = new ArrayList<Integer>();
solve(results, list, num, 0, target);
return results;
}

private void solve(ArrayList<ArrayList<Integer>> results,
ArrayList<Integer> list, int[] num, int i, int target) {
if (target < 0) {
return;
}
if (target == 0) {
results.add(new ArrayList<Integer>(list));
return;
}
for (int j = i; j < num.length && num[j] <= target; ++j) {
list.add(num[j]);
solve(results, list, num, j + 1, target - num[j]);
list.remove(list.size() - 1);
while (j < num.length - 1 && num[j] == num[j + 1]) {
++j;
}
}
}
}