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LeetCode Solutions : Combination Sum I & II
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
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