Leetcode: Combination Sum II
This problem is defined as follows:
Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to target.
Each number in candidates may only be used once in the combination.
Note: The solution set must not contain duplicate combinations.
Here are some examples pertaining to this LeetCode Question:
Input: candidates = [10,1,2,7,6,1,5], target = 8 Output: [ [1,1,6], [1,2,5], [1,7], [2,6] ]
Input: candidates = [2,5,2,1,2], target = 5 Output: [ [1,2,2], [5] ]
And the output is as follows:
class Solution {
public List < List < Integer >> combinationSum2(int[] candidates, int target) {
Arrays.sort(candidates); //sort the lesser values to be earlier in this array.
List < List < Integer >> res = new ArrayList < List < Integer >> (); //set a ArrayLists of lists to store the paths
List < Integer > path = new ArrayList < Integer > (); //This is the current burner path
dfs_com(candidates, 0, target, path, res); //this is the bfs method for the dfs
return res;
}
public void dfs_com(int[] cand, int cur, int target, List < Integer > path, List < List < Integer >> res) {
//if there is nothing to add, add the path to the list, and the method is done
//or call the previous recursive method in the stack.
if (target == 0) {
res.add(new ArrayList(path));
return;
}
//return if there is an invalid result, and remove.
if (target < 0) return;
//iterate through and perform a recursion from the current integer index.
for (int i = cur; i < cand.length; i++) {
//make sure that these numbers are not the same.
if (i > cur && cand[i] == cand[i - 1]) continue;
//add the number to the path
path.add(path.size(), cand[i]);
//perform bfs, to check if path is valid, and how to find new paths
dfs_com(cand, i + 1, target - cand[i], path, res);
//if there is an invalid path or a stack overflow, remove the result.
path.remove(path.size() - 1);
}
}
}


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