leecode_300 Longest Increasing Subsequence

最新推荐文章于 2024-09-11 15:54:46 发布

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最新推荐文章于 2024-09-11 15:54:46 发布

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本文介绍了一种求解最长递增子序列长度的问题，并提供了一个使用Java实现的示例。该算法通过TreeSet实现了O(n log n)的时间复杂度。

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?

c++的写过了，来一发java版的实现：

public class Solution {
    public int lengthOfLIS(int[] nums) {
        
        TreeSet<Integer> ts= new TreeSet<Integer>();
        
        for (int i=0;i<nums.length;i++)
        	  ts.add(Integer.MIN_VALUE);
        	  
        int len=0;
        
        for (int i=0;i<nums.length;i++){
        	    Integer ee=ts.ceiling(nums[i]);
        	    if (ee!=null){
        	    	    ts.remove(ee);
        	    	    ts.add(nums[i]);
        	    }
        	    else{
        	    	    ts.add(nums[i]);
        	    	    len++;
        	    }
        	    	      
        }
       
       return len; 
    }
}