Merge pull request #2227 from 8804who/main

[8804who] WEEK 07 solutions

Author: 8804who

longest-substring-without-repeating-characters/8804who.py

@@ -0,0 +1,16 @@
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        start = 0
+        end = 0
+        answer = 0
+        character_set = set()
+        while end<len(s):
+            while s[end] in character_set:
+                character_set.remove(s[start])
+                start += 1
+            character_set.add(s[end])
+            if answer < end-start+1:
+                answer = end-start+1
+            end += 1
+        return answer
+    

number-of-islands/8804who.py

@@ -0,0 +1,23 @@
+class Solution:
+    def numIslands(self, grid: List[List[str]]) -> int:
+        n, m = len(grid), len(grid[0])
+
+        answer = 0
+        moves = [[-1,0],[1,0],[0,1],[0,-1]]
+        visited = [[False for _ in range(m)] for _ in range(n)]
+        def dfs(y, x):
+            for move in moves:
+                moved_y, moved_x = y+move[0], x+move[1]
+                if n > moved_y >= 0 and m > moved_x >= 0:
+                    if grid[moved_y][moved_x] == '1' and not visited[moved_y][moved_x]:
+                        visited[moved_y][moved_x] = True
+                        dfs(moved_y, moved_x)
+        
+        for i in range(n):
+            for j in range(m):
+                if not visited[i][j] and grid[i][j] == '1':
+                    visited[i][j] = True
+                    answer += 1
+                    dfs(i, j)
+        return answer
+    

reverse-linked-list/8804who.py

@@ -0,0 +1,16 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        node = head
+        reversed_node = None
+        while node:
+            val = node.val
+            reversed_node = ListNode(val=val, next=reversed_node)
+            node = node.next
+        return reversed_node
+        
+    

set-matrix-zeroes/8804who.py

@@ -0,0 +1,18 @@
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        """
+        Do not return anything, modify matrix in-place instead.
+        """
+        temp = []
+        n, m = len(matrix), len(matrix[0])
+        for i in range(n):
+            for j in range(m):
+                if matrix[i][j] == 0:
+                    temp.append((i, j))
+        
+        for t in temp:
+            for i in range(n):
+                matrix[i][t[1]] = 0
+            for j in range(m):
+                matrix[t[0]][j] = 0
+    

unique-paths/8804who.py

@@ -0,0 +1,14 @@
+class Solution:
+    def uniquePaths(self, m: int, n: int) -> int:
+        dp = [[0 for _ in range(n)] for _ in range(m)]
+        dp[0][0] = 1
+
+        for i in range(m):
+            for j in range(n):
+                if i-1>=0:
+                    dp[i][j]+=dp[i-1][j]
+                if j-1>=0:
+                    dp[i][j]+=dp[i][j-1]
+
+        return dp[-1][-1]
+