Longest substring without repeating characters.

Author: recherst

Easy/3.Longest Substring Without Repeating Characters.playground/Contents.swift

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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.
+ */
+class Solution {
+    func lengthOfLongestSubstring(_ s: String) -> Int {
+        guard !s.isEmpty else { return 0 }
+        var max = 0
+        var current = 0
+        var subStrArr = [s.first!]
+        for e in s {
+            if !subStrArr.contains(e) {
+                subStrArr.append(e)
+                current += 1
+                if current > max {
+                    max = current
+                }
+            } else {
+                let firstIndex: Int = subStrArr.firstIndex(of: e)!
+                subStrArr = Array(subStrArr[(firstIndex + 1)...])
+                current = subStrArr.count
+                
+                subStrArr.append(e)
+                current += 1
+                if current > max {
+                    max = current
+                }
+            }
+        }
+        return current > max ? current : max
+    }
+}
+
+let s = Solution()
+let r = s.lengthOfLongestSubstring("abcabcbb")
+print(r)

Easy/3.Longest Substring Without Repeating Characters.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Easy/3.Longest Substring Without Repeating Characters.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -106,3 +106,4 @@
 #### Medium
 
 1. [Min Stack](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/155.Min%20Stack.playground/Contents.swift)
+1. [Longest Substring Without Repeating Characters](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/3.Longest%20Substring%20Without%20Repeating%20Characters.playground/Contents.swift)