Longest Increasing Subsequence

lc 300

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.

dp, 最长上升序列，当i比j小或者想同时，这里最长只能是1了，只有i比j大，才能更新

public class Solution {
    public int lengthOfLIS(int[] nums) {
        if (nums == null || nums.length == 0 ) return 0;
        int res = 1;
        int[] f = new int[nums.length];
        f[0] = 1;
        for (int i = 1 ; i < nums.length; i++){
            for ( int j = 0; j < i; j++){
                if(nums[i] <= nums[j]){
                    f[i] = Math.max(1, f[i]);
                    continue;
                }else{
                    f[i] =Math.max(f[i], f[j] + 1);
                    res = Math.max(res, f[i]);
                }
            }
        }
        return res;
    }
}