feat: add nim-lang solution to lc problem: No.0003.Longest Substring (#574)

Author: yozachar

solution/0000-0099/0003.Longest Substring Without Repeating Characters/README.md

@@ -202,6 +202,28 @@ func max(x, y int) int {
 }
 ```
 
+### **Nim**
+
+```nim
+proc lengthOfLongestSubstring(s: string): int =
+  var
+    i = 0
+    j = 0
+    res = 0
+    literals: set[char] = {}
+
+  while i < s.len:
+    while s[i] in literals:
+      if s[j] in literals:
+        excl(literals, s[j])
+      j += 1
+    literals.incl(s[i]) # Uniform Function Call Syntax f(x) = x.f
+    res = max(res, i - j + 1)
+    i += 1
+
+  result = res # result has the default return value
+```
+
 ### **...**
 
 ```

solution/0000-0099/0003.Longest Substring Without Repeating Characters/README_EN.md

@@ -184,6 +184,28 @@ func max(x, y int) int {
 }
 ```
 
+### **Nim**
+
+```nim
+proc lengthOfLongestSubstring(s: string): int =
+  var
+    i = 0
+    j = 0
+    res = 0
+    literals: set[char] = {}
+
+  while i < s.len:
+    while s[i] in literals:
+      if s[j] in literals:
+        excl(literals, s[j])
+      j += 1
+    literals.incl(s[i]) # Uniform Function Call Syntax f(x) = x.f
+    res = max(res, i - j + 1)
+    i += 1
+
+  result = res # result has the default return value
+```
+
 ### **...**
 
 ```

solution/0000-0099/0003.Longest Substring Without Repeating Characters/Solution.nim

@@ -0,0 +1,19 @@
+proc lengthOfLongestSubstring(s: string): int =
+  var
+    i = 0
+    j = 0
+    res = 0
+    literals: set[char] = {}
+
+  while i < s.len:
+    while s[i] in literals:
+      if s[j] in literals:
+        excl(literals, s[j])
+      j += 1
+    literals.incl(s[i]) # Uniform Function Call Syntax f(x) = x.f
+    res = max(res, i - j + 1)
+    i += 1
+
+  result = res # result has the default return value
+
+echo lengthOfLongestSubstring("abcddabcf")