[Leo] 9th Week solutions

Author: leokim0922

design-add-and-search-words-data-structure/Leo.py

@@ -0,0 +1,48 @@
+class TrieNode:
+    def __init__(self):
+        self.links = {}
+        self.end = False
+
+
+class WordDictionary:
+    def __init__(self):
+        self.root = TrieNode()
+        self.maxL = 0
+
+    def addWord(self, word: str) -> None:
+        node = self.root
+        l = 0
+
+        for w in word:
+            if w not in node.links:
+                node.links[w] = TrieNode()
+            node = node.links[w]
+            l += 1
+
+        self.maxL = max(self.maxL, l)
+        node.end = True
+
+        ## TC: O(len(word)), SC: O(1)
+
+    def search(self, word: str) -> bool:
+        if len(word) > self.maxL:
+            return False
+
+        def helper(index, node):
+            for inn in range(index, len(word)):
+                c = word[inn]
+                if c == ".":
+                    for child in node.links.values():
+                        if helper(inn + 1, child):
+                            return True
+                    return False
+                else:
+                    if c not in node.links:
+                        return False
+                    node = node.links[c]
+
+            return node.end
+
+        return helper(0, self.root)
+
+        ## TC: O(num(node)), SC: O(len(word))

number-of-islands/Leo.py

@@ -0,0 +1,25 @@
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        res = 0
+        rows, cols, = len(grid), len(grid[0])
+
+        def dfs(x, y):
+            if x < 0 or y < 0 or x >= rows or y >= cols or grid[x][y] == "0":
+                return
+
+            if grid[x][y] == "1":
+                grid[x][y] = "0"
+                dfs(x + 1, y)
+                dfs(x - 1, y)
+                dfs(x, y + 1)
+                dfs(x, y - 1)
+
+        for i in range(rows):
+            for j in range(cols):
+                if grid[i][j] == "1":
+                    dfs(i, j)
+                    res += 1
+
+        return res
+
+        ## TC & SC: O(m*n)