Leetcode Java-Combination Sum
Title:
iven a set of candidate numbers (C) (without duplicates) 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.
- 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] ]
这道题利用回溯即可。
solution:
public class Solution {
List<List<Integer>> ans = new ArrayList<List<Integer>>();
int[] cans = {};
public List<List<Integer>> combinationSum(int[] candidates, int target) {
this.cans = candidates;
Arrays.sort(cans);
backTracking(new ArrayList(), 0, target);
return ans;
}
public void backTracking(List<Integer> cur, int from, int target) {
if (target == 0) {
List<Integer> list = new ArrayList<Integer>(cur);
ans.add(list);
} else {
for (int i = from; i < cans.length && cans[i] <= target; i++) {
cur.add(cans[i]);
backTracking(cur, i, target - cans[i]);
cur.remove(new Integer(cans[i]));
}
}
}
}
posted on 2017-09-29 15:18 sichenzhao 阅读(155) 评论(0) 编辑 收藏 举报