Added Leetcode Longest Substring Without Repeating Characters problem (dubesar#615)

Author: sourabhvarshney111

LeetCode/Top 100 Liked/Longest Substring Without Repeating Characters/Solution.java

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+import java.util.*;
+
+class Solution {
+    public int lengthOfLongestSubstring(String s) {
+        // Map to store the character and its latest idx while traversing the string from left to right
+        Map<Character, Integer> map = new HashMap<>();
+        int max=0;
+
+        // i == start position of window
+        // j = curr/end position of window being explored
+        for(int i=0, j=0; j < s.length(); j++){
+            char c = s.charAt(j);
+            // If the current character has previously been seen and
+            // the previous occurrence (idx) of the char >= the starting position of the window to be explored (i)
+            if(map.containsKey(c) && map.get(c) >= i)
+                i = map.get(c) + 1;
+            int currWindow = j-i+1;
+            max = Math.max(currWindow, max);
+            map.put(c, j);
+        }
+        return max;
+    }
+}

LeetCode/Top 100 Liked/Longest Substring Without Repeating Characters/problem_statement.txt

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+Given a string s, find the length of the longest substring without repeating characters.
+
+Example 1:
+Input: s = "abcabcbb"
+Output: 3
+Explanation: The answer is "abc", with the length of 3.
+
+Example 2:
+Input: s = "bbbbb"
+Output: 1
+Explanation: The answer is "b", with the length of 1.
+
+Example 3:
+Input: s = "pwwkew"
+Output: 3
+Explanation: The answer is "wke", with the length of 3.
+Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
+
+
+Constraints:
+0 <= s.length <= 5 * 104
+s consists of English letters, digits, symbols and spaces.