Copy List with Random Pointer/ Word Break

Author: gavinfish

138 Copy List with Random Pointer.py

@@ -0,0 +1,39 @@
+'''
+A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.
+
+Return a deep copy of the list.
+'''
+
+# Definition for singly-linked list with a random pointer.
+class RandomListNode(object):
+    def __init__(self, x):
+        self.label = x
+        self.next = None
+        self.random = None
+
+
+class Solution(object):
+    def copyRandomList(self, head):
+        """
+        :type head: RandomListNode
+        :rtype: RandomListNode
+        """
+        if not head:
+            return None
+        visited = dict()
+        node = head
+        while node:
+            visited[node] = RandomListNode(node.label)
+            node = node.next
+
+        visited[None] = None
+        node = head
+        while node:
+            visited[node].next = visited[node.next]
+            visited[node].random = visited[node.random]
+            node = node.next
+        return visited[head]
+
+
+if __name__ == "__main__":
+    None

139 Word Break.py

@@ -0,0 +1,30 @@
+'''
+Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.
+
+For example, given
+s = "leetcode",
+dict = ["leet", "code"].
+
+Return true because "leetcode" can be segmented as "leet code".
+'''
+
+class Solution(object):
+    def wordBreak(self, s, wordDict):
+        """
+        :type s: str
+        :type wordDict: Set[str]
+        :rtype: bool
+        """
+        n = len(s)
+        dp = [False] * (n + 1)
+        dp[0] = True
+        for i in range(n):
+            for j in range(i, -1, -1):
+                if dp[j] and s[j:i + 1] in wordDict:
+                    dp[i + 1] = True
+                    break
+        return dp[n]
+
+
+if __name__ == "__main__":
+    assert Solution().wordBreak("leetcode", {"leet", "code"}) == True