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, … , a_k) must be in non-descending order. (ie, a₁ ≤ a₂ ≤ … ≤ a_k).
• 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;
			}
		}
	}
}