leetcode之Combination Sum
2014-08-22 15:17
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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
A solution set is:
思路:典型的递归程序,对每次遍历,取当前数和不取当前数进行遍历。
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
target
A solution set is:
如果是求总数,而且不需要去除重复,可以看这里
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
2,3,6,7and target
7,
A solution set is:
[7]
[2, 2, 3]
思路:典型的递归程序,对每次遍历,取当前数和不取当前数进行遍历。
class Solution { public: void combinationSum(vector<int>& candidates,int index,int currentSum,int target,vector<int>& path) { if(currentSum == target) { res.push_back(path); return; } int length = candidates.size(); if(index == length || currentSum > target)return; path.push_back(candidates[index]); combinationSum(candidates,index,currentSum+candidates[index],target,path);//重复添加当前节点 path.pop_back(); combinationSum(candidates,index+1,currentSum,target,path);//跳过当前节点 } vector<vector<int> > combinationSum(vector<int> &candidates, int target) { sort(candidates.begin(),candidates.end()); vector<int> path; combinationSum(candidates,0,0,target,path); return res; } private: vector<vector<int> > res; };
Combination Sum II
Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numberssums 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
10,1,2,7,6,1,5and
target
8,
A solution set is:
[1, 7]
[1, 2, 5]
[2, 6]
[1, 1, 6]
class Solution { public: void combinationSum2(vector<int>& num,int index,int currentSum,int target,vector<int>& path) { if(currentSum == target) { hash.insert(path);//防止重复 return; } int length = num.size(); if(index == length || currentSum > target)return; path.push_back(num[index]); combinationSum2(num,index+1,currentSum+num[index],target,path);//取当前节点 path.pop_back(); combinationSum2(num,index+1,currentSum,target,path);//不取当前节点 } vector<vector<int> > combinationSum2(vector<int> &num, int target) { sort(num.begin(),num.end()); vector<int> path; combinationSum2(num,0,0,target,path); vector<vector<int> > res(hash.begin(),hash.end()); return res; } private: set<vector<int> > hash; };
如果是求总数,而且不需要去除重复,可以看这里
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