LeetCode Solutions : Combination Sum I & II

標籤：leetcode   java   algorithms   datastructure   np   

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

The same repeated number may be chosen from C unlimited number of times.

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 2,3,6,7 and target 7, 
A solution set is: 
[7] 
[2, 2, 3] 

public class Solution {    public ArrayList<ArrayList<Integer>> combinationSum(int[] candidates, int target) {        ArrayList<ArrayList<Integer>> results=new ArrayList<ArrayList<Integer>>();if(candidates==null)return results;Arrays.sort(candidates);helper(candidates,0,target,results,new ArrayList<Integer>());return results;    }private void helper(int[] candidates,int start,int target,ArrayList<ArrayList<Integer>> results,ArrayList<Integer> temp){if(target==0){results.add(new ArrayList<Integer>(temp));return;}for(int i=start;i<candidates.length;i++){if(candidates[i]<=target){temp.add(candidates[i]);helper(candidates,i,target-candidates[i],results,temp);temp.remove(temp.size()-1);}}}}

Combination Sum II 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] 

public class Solution {    public ArrayList<ArrayList<Integer>> combinationSum2(int[] num, int target) {        ArrayList<ArrayList<Integer>> results=new ArrayList<ArrayList<Integer>>();if(num==null)return results;Arrays.sort(num);helper(num,0,target,results,new ArrayList<Integer>());return results;    }private void helper(int[] candidates,int start,int target, ArrayList<ArrayList<Integer>> results,ArrayList<Integer> temp){if(target==0){results.add(new ArrayList<Integer>(temp));return;}for(int i=start;i<candidates.length;i++){if(i>start&&candidates[i]==candidates[i-1])continue;if(candidates[i]<=target){temp.add(candidates[i]);helper(candidates,i+1,target-candidates[i],results,temp);temp.remove(temp.size()-1);}}}}

LeetCode Solutions : Combination Sum I & II