标签:算法
k-sum问题都可以有2-sum引申出来解决,但是时间复杂度为O(n^k-1)。应该要用哈希解决才好的,之后再看看
class Solution{ private: vector<vector<int> > ans; public: vector<vector<int> >fourSum(vector<int> &num, int target){ sort(num.begin(),num.end()); ans.clear(); for(int i = 0; i < num.size(); ++i) { if(i > 0 && num[i] == num[i-1]) continue; for(int j = i+1; j < num.size(); ++j){ if(j > i+1 && num[j] == num[j-1]) continue; int k = j+1; int t = num.size()-1; while(k < t){ if(k > j+1 && num[k] == num[k-1]){ k++; continue; } if(t < num.size()-1 && num[t] == num[t+1]){ t--; continue; } int sum = num[i]+num[j]+num[k]+num[t]; if(sum == target){ vector<int>a; a.push_back(num[i]); a.push_back(num[j]); a.push_back(num[k]); a.push_back(num[t]); ans.push_back(a); k++; } else if(sum < target) k++; else t--; } } } return ans; } };
标签:算法
原文地址:http://blog.csdn.net/sina012345/article/details/42788097