2981

Author: theforestvn88

2901-3000/2981_find_longest_special_substring_that_occurs_thrice_i.rb

@@ -0,0 +1,53 @@
+# @param {String} s
+# @return {Integer}
+def maximum_length(s)
+    max = -1
+    counter = Hash.new(0)
+    (0...s.length).each { |i|
+        (i...s.length).each { |j|
+            break if s[j] != s[i]
+            
+            sub = s[i..j]
+            counter[sub] += 1
+            if counter[sub] >= 3
+                max = [max, j-i+1].max
+            end
+        }
+    }
+
+    max
+end
+
+# optimize
+def maximum_length(s)
+    counter = Array.new(26) { Array.new(s.length+1, 0) }
+  
+    prev = nil
+    len = 1
+    s.each_char { |c|
+        if prev == c
+            counter[c.ord - 97][len += 1] += 1
+        else
+            len = 1
+            counter[c.ord - 97][len] += 1
+            prev = c
+        end
+    }
+  
+    max = -1
+    (0..25).each { |i|
+        len = s.length
+        # a substring with len has 2 substring with len-1, prefix and suffix
+        count = 0
+        while len >= 1
+            count += counter[i][len]
+            if count >= 3
+                max = len if max < len
+                break
+            end
+            len -= 1 
+        end
+    }
+  
+    max
+end