[leetcode] Longest Substring with At Most Two Distinct Characters

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public class Solution { public int lengthOfLongestSubstringTwoDistinct(String s) { if (s == null || s.length() == 0) return 0; if (s.length() == 1) return 1; char c1 = s.charAt(0); char c2 = s.charAt(1); int i1 = 0; int i2 = 0; int length = 2; for (int i = 2; i < s.length(); i++){ char current = s.charAt(i); if (current != c1 && current != c2){ c1 = current; c2 = s.charAt(i-1); i1 = i; i2 = i-1; while (i2 >= 0&&s.charAt(i2) == c2){ i2--; } i2++; } length = Math.max(length, i-Math.min(i1, i2)+1); } return length; } }