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LeetCode Combination Sum

时间:2015-04-25 18:14:19      阅读:104      评论:0      收藏:0      [点我收藏+]

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这题居然没有记录,写一下吧:

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] 

 1 // 17:10
 2 class Solution {
 3 private:
 4     vector<vector<int> > res;
 5 public:
 6     vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
 7         res.clear();
 8         sort(candidates.begin(), candidates.end());
 9         vector<int> path;
10         dfs(candidates, candidates.size() - 1, target, path);
11         return res;
12     }
13     
14     void dfs(vector<int>& candidates, int pos, int target, vector<int>& path) {
15         if (target == 0) {
16             res.push_back(path);
17             reverse(res.back().begin(), res.back().end());
18             return;
19         }
20         if (target < 0 || pos < 0) {
21             return;
22         }
23         
24         int curv = candidates[pos];
25         
26         // don‘t use current value
27         dfs(candidates, pos - 1, target, path);
28         int cnt = 0;
29         while (target > 0) {
30             path.push_back(curv);
31             target -= curv;
32             dfs(candidates, pos - 1, target, path);
33             cnt++;
34         }
35         
36         path.resize(path.size() - cnt);
37     }
38 };

 

LeetCode Combination Sum

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原文地址:http://www.cnblogs.com/lailailai/p/4456254.html

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