Palindrome Partitioning

NeetCode/palindrome-partitioning/step1.py

@@ -0,0 +1,92 @@
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
+        res = []
+        partitions = []
+
+        def check_palindrome(s):
+            if not s:
+                return False
+
+            front = 0
+            back = len(s) - 1
+            while front <= back and s[front] == s[back]:
+                front += 1
+                back -= 1
+            return front > back
+
+        def append_palindrome(index, partition):
+            if index == len(s):
+                if not check_palindrome(partition):
+                    return
+                res.append(partitions.copy() + [partition])
+                return
+
+            append_palindrome(index + 1, partition + s[index])
+
+            if check_palindrome(partition):
+                partitions.append(partition)
+                append_palindrome(index + 1, s[index])
+                partitions.pop()
+
+        append_palindrome(0, "")
+        return res
+
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
+        res = []
+        partitions = []
+
+        def check_palindrome(s):
+            if not s:
+                return False
+
+            front = 0
+            back = len(s) - 1
+            while front <= back and s[front] == s[back]:
+                front += 1
+                back -= 1
+            return front > back
+
+        def append_palindrome(index, partition):
+            if index == len(s):
+                if not check_palindrome(partition):
+                    return
+                res.append(partitions.copy() + [partition])
+                return
+
+            append_palindrome(index + 1, partition + s[index])
+
+            if check_palindrome(partition):
+                partitions.append(partition)
+                append_palindrome(index + 1, s[index])
+                partitions.pop()
+
+        append_palindrome(0, "")
+        return res
+
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
+        res = []
+        partitions = []
+
+        def check_palindrome(s, left, right):
+            while left < right:
+                if s[left] != s[right]:
+                    return False
+                left += 1
+                right -= 1
+            return True
+
+        def append_palindromes(index):
+            if index == len(s):
+                res.append(partitions.copy())
+                return
+
+            for j in range(index, len(s)):
+                if check_palindrome(s, index, j):
+                    partitions.append(s[index : j + 1])
+                    append_palindromes(j + 1)
+                    partitions.pop()
+
+        append_palindromes(0)
+        return res

NeetCode/palindrome-partitioning/step3.py

@@ -0,0 +1,65 @@
+# time: O(2^n * n) generating all possible substrings, check if it is palindrome
+# space: O(n)
+
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
+        res = []
+        palindromes = []
+
+        def check_palindrome(s, left, right):
+            while left < right:
+                if s[left] != s[right]:
+                    return False
+                left += 1
+                right -= 1
+            return True
+
+        def append_palindrome(index):
+            if index == len(s):
+                res.append(palindromes.copy())
+                return
+
+            for j in range(index, len(s)):
+                if check_palindrome(s, index, j):
+                    palindromes.append(s[index : j + 1])
+                    append_palindrome(j + 1)
+                    palindromes.pop()
+
+        append_palindrome(0)
+        return res
+
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
+        res = []
+        palindromes = []
+
+        def check_palindrome(s):
+            if not s:
+                return False
+
+            left = 0
+            right = len(s) - 1
+            while left < right:
+                if s[left] != s[right]:
+                    return False
+                left += 1
+                right -= 1
+            return True
+
+        def append_partitions(index, partition):
+            if index == len(s):
+                if not check_palindrome(partition):
+                    return
+                res.append(palindromes.copy() + [partition])
+                return
+
+            partition += s[index]
+            append_partitions(index + 1, partition)
+
+            if check_palindrome(partition):
+                palindromes.append(partition)
+                append_partitions(index + 1, "")
+                palindromes.pop()
+
+        append_partitions(0, "")
+        return res