Leetcode Everyday: 340. Longest Substring with At Most K Distinct Characters

https://leetcode.com/problems/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

public class Solution {    public int lengthOfLongestSubstringKDistinct(String s, int k) {        if(k==0) return 0;        char[] cArr = s.toCharArray();        int[] occ = new int[128];        int start = 0;        int dis = 0;        int maxLen = 0;        for(int i = 0; i<cArr.length; i++){            if(occ[cArr[i]]==0){                occ[cArr[i]]++;dis++;                if(dis>k){                    while(--occ[cArr[start++]] != 0);                }            }else{                occ[cArr[i]]++;            }            if(i-start+1>maxLen) maxLen = i-start+1;        }        return maxLen;    }}

The idea is to keep a sliding window using two pointers. The first pointer is start, and the second pointer is i. we record how many times does a char occurs in the window. When we encounter a new char and there are k+1 chars in the window, we increase the start pointer and make correspond changes in the occurrence array, util we find some chars  occurrence is from 1->0, this means a char has been removed out of the window.

asd