340. Longest Substring with At Most K Distinct Characters

Given a string, find the length of the longest substring T that contains at most k distinct characters.

For example, Given s = “eceba” and k = 2,

T is "ece" which its length is 3.

本题和Longest Substring with At Most Two Distinct Characters很类似，代码如下：

public class Solution {
    public int lengthOfLongestSubstringKDistinct(String s, int k) {
        int len = 0;
        int lo = 0;
        int hi = 0;
        if(s.length()==0) return len;
        Map<Character,Integer> map = new HashMap<>();
        while(hi<s.length()){
            if(map.size()<=k){
                char c = s.charAt(hi);
                map.put(c,hi);
                hi++;
            }
            if(map.size()>k){
                int leftmost = s.length();
                for(int i:map.values()){
                    leftmost= Math.min(leftmost,i);
                }
                char c = s.charAt(leftmost);
                map.remove(c);
                lo = leftmost+1;
            }
            len = Math.max(len,hi-lo);
        }
        return len;
    }
}