Repeated substring pattern.

Author: recherst

Easy/459.Repeated Substring Pattern.playground/Contents.swift

@@ -0,0 +1,49 @@
+/**
+ Given a string s, check if it can be constructed by taking a substring of it and appending multiple copies of the substring together.
+
+  
+
+ Example 1:
+ Input: s = "abab"
+ Output: true
+ Explanation: It is the substring "ab" twice.
+ 
+ Example 2:
+ Input: s = "aba"
+ Output: false
+ 
+ Example 3:
+ Input: s = "abcabcabcabc"
+ Output: true
+ Explanation: It is the substring "abc" four times or the substring "abcabc" twice.
+  
+
+ Constraints:
+ - 1 <= s.length <= 104
+ - s consists of lowercase English letters.
+ */
+class Solution {
+    func repeatedSubstringPattern(_ s: String) -> Bool {
+        let arr: [Character] = s.map { $0 }
+        var i = 1
+        var j = 0
+        let n = s.count
+        var dp: [Int] = Array(repeating: 0, count: n + 1)
+        while i < n {
+            if arr[i] == arr[j] {
+                i += 1
+                j += 1
+                dp[i] = j
+            } else if j == 0 {
+                i += 1
+            } else {
+                j = dp[j]
+            }
+        }
+        return dp[n] % (n - dp[n]) == 0 && dp[n] != 0
+    }
+}
+
+let s = Solution()
+let r = s.repeatedSubstringPattern("bb")
+print(r)

Easy/459.Repeated Substring Pattern.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?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/459.Repeated Substring Pattern.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -92,6 +92,7 @@
 88. [Find All Numbers Disappeared in an Array](c)
 89. [Minimum Moves to Equal Array Elements](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/448.Minimum%20Moves%20toEqual%20Array%20Elements.playground/Contents.swift)
 90. [Assign Cookies](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/455.Assign%20Cookies.playground/Contents.swift)
+91. [Repeated Substring Pattern](https://github.com/recherst/leetcode-algtorithm/blob/main/Easy/459.Repeated%20Substring%20Pattern.playground/Contents.swift)
 
 #### Medium