Longest Increasing Subsequence
Total Accepted: 9797 Total Submissions: 30801 Difficulty: Medium
Given an unsorted array of integers, find the length of longest increasing subsequence.
For example,
Given [10, 9, 2, 5, 3, 7, 101, 18]
,
The longest increasing subsequence is [2, 3, 7, 101]
, therefore the length is 4
. Note that there may be more than one LIS combination, it is only necessary for you to return the length.
Your algorithm should run in O(n2) complexity.
Follow up: Could you improve it to O(n log n) time complexity?
1.o(n*n)
class Solution { public: int lengthOfLIS(vector<int>& nums) { int n = nums.size(); int res = n==0 ? 0 : 1; vector<int> help(n,1); for(int i=1;i<n;i++){ for(int j=0;j<i;j++){ if(nums[j] < nums[i]){ help[i] = max(help[i],help[j]+1); res = max(res,help[i]); } } } return res; } };
2.o(n*lgn)
class Solution { public: int lengthOfLIS(vector<int>& nums) { int n = nums.size(); vector<int> help; for(int i=0;i<n;i++){ auto iter = lower_bound(help.begin(),help.end(),nums[i]); if(iter == help.end()){ help.push_back(nums[i]); }else{ *iter=nums[i]; } } return help.size(); } };
写者:zengzy
出处: http://www.cnblogs.com/zengzy
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