feat: Add LongestSubstringWithAtMostTwoDistinct solution with string,map

Author: hyeoni90

src/main/java/com/hyeonah/javalabs/algorithm/top50coding/stringAndArray/LongestSubstringWithAtMostTwoDistinct.java

@@ -0,0 +1,61 @@
+package com.hyeonah.javalabs.algorithm.top50coding.stringAndArray;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Created by hyeoni90 on 2021-02-15
+ *
+ * ex1)
+ * input: "ccaabbb"
+ * output: 5 (length of `aabbb`)
+ *
+ * ex2)
+ * input: "eceba"
+ * output: 3 (length of `ece`)
+ *
+ * keyword >
+ * Map, Two Pointer, Math.max
+ * (start, end 를 알아야하며, end-start 한 length 를 알아야 한다.)
+ */
+public class LongestSubstringWithAtMostTwoDistinct {
+
+ public static void main(final String[] args) {
+ final String str = "ccaabbb";
+ final String str1 = "eceba";
+ System.out.println(new LongestSubstringWithAtMostTwoDistinct().solution(str));
+ System.out.println(new LongestSubstringWithAtMostTwoDistinct().solution(str1));
+ }
+
+ private int solution(final String str) {
+ int start = 0;
+ int count = 0; // 문자열의 문자 갯수..2
+ int maxLength = 0;
+
+ // 문자열의 문자과 문자 갯수
+ final Map<Character, Integer> map = new HashMap<>();
+
+ for (int i = 0; i < str.length(); i++) {
+ final char endChar = str.charAt(i);
+ map.put(endChar, map.getOrDefault(endChar, 0) + 1); // cß=2, a=2, b=3
+
+ if (map.get(endChar) == 1) {
+ count++;
+ }
+
+ // 기존에 담겨 있던 문자을 삭제한다.
+ if (count > 2) {
+ final char startChar = str.charAt(start); // c
+ map.put(startChar, map.get(startChar) - 1);
+ if (map.get(startChar) == 0) {
+ count--;
+ }
+ start++;
+ }
+
+ maxLength = Math.max(maxLength, i - start + 1);
+ }
+
+ return maxLength;
+ }
+}