Combination Sum II

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Given a collection of candidate numbers (C) and a target number (T), find all unique combinations inC 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] 

答案

public class Solution {    int[] candidates;    public List<List<Integer>> combinationSum(int index ,int target)    {        List<List<Integer>> result=new LinkedList<List<Integer>>();        if(index>=candidates.length||candidates[index]>target)        {            return result;        }        List<Integer> p=new LinkedList<Integer>();        int end;        for(end=index;end<candidates.length;end++)        {            if(candidates[end]!=candidates[index])            {                break;            }        }        int times=end-index;        for(int time=0;time<=times;time++)        {            if(target==0)            {                result.add(p);                break;            }            List<List<Integer>> next=combinationSum(end,target);            if(next.size()>0)            {                for(List<Integer> list:next)                {                    List<Integer> pList=new LinkedList<Integer>();                    pList.addAll(p);                    pList.addAll(list);                    result.add(pList);                }            }            p.add(candidates[index]);            target-=candidates[index];        }        return result;    }    public List<List<Integer>> combinationSum2(int[] candidates, int target) {        List<List<Integer>> result=new LinkedList<List<Integer>>();        if(candidates==null||target<=0)        {            return result;        }        Arrays.sort(candidates);        this.candidates=candidates;        return combinationSum(0,target);    }}

ArrayBacktracking

Combination Sum II