159 Longest Substring with At Most Two Distinct Characters
这两题有一个 trick 和 Minimum Window Substring 非常
像,就是维护一个 "curCount" 代表目前 (i,j) 之间 match 上
的数量,而通过 hash[] 的正负充当计数器的作用
Given a string, find the length of the longest substring T that contains at most 2 distinct characters. For example, Given s = “eceba”, T is "ece" which its length is 3.
参照 k characters: http://www.cnblogs.com/apanda009/p/7261514.html
linkedhashmap可以用来解stream
public int lengthOfLongestSubstringTwoDistinct(String s) { int maxSize = 0; int j = 0; int[] hash = new int[256]; int distinctCount = 0; for(int i = 0; i < s.length(); i++){ while(j < s.length()){ if(distinctCount == 2 && hash[s.charAt(j)] == 0) break; if(hash[s.charAt(j)] == 0) distinctCount ++; hash[s.charAt(j++)]++; } if(j - i > maxSize){ maxSize = j - i; } hash[s.charAt(i)]--; if(hash[s.charAt(i)] == 0) distinctCount --; } return maxSize; }
可以用hashmap 来替换hash[]
字符串内连续匹配, 连续计数, 连续求最值问题常用窗口类型的指针, 状态常用计数和, 单个计数, hash 中是否存在, 遍历过? 表示, 看题目要求