[printjin-gmailcom] Week 7 Solutions

longest-substring-without-repeating-characters/printjin-gmailcom.py

@@ -0,0 +1,14 @@
+class Solution:
+    def lengthOfLongestSubstring(self, s):
+        char_set = set()
+        left = 0
+        max_len = 0
+
+        for right in range(len(s)):
+            while s[right] in char_set:
+                char_set.remove(s[left])
+                left += 1
+            char_set.add(s[right])
+            max_len = max(max_len, right - left + 1)
+
+        return max_len

number-of-islands/printjin-gmailcom.py

@@ -0,0 +1,24 @@
+class Solution:
+    def numIslands(self, grid):
+        if not grid:
+            return 0
+
+        rows, cols = len(grid), len(grid[0])
+        count = 0
+
+        def dfs(r, c):
+            if r < 0 or c < 0 or r >= rows or c >= cols or grid[r][c] == "0":
+                return
+            grid[r][c] = "0"
+            dfs(r+1, c)
+            dfs(r-1, c)
+            dfs(r, c+1)
+            dfs(r, c-1)
+
+        for r in range(rows):
+            for c in range(cols):
+                if grid[r][c] == "1":
+                    dfs(r, c)
+                    count += 1
+
+        return count

reverse-linked-list/printjin-gmailcom.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):
+        prev = None
+        current = head
+        while current:
+            nxt = current.next
+            current.next = prev
+            prev = current
+            current = nxt
+        return prev

set-matrix-zeroes/printjin-gmailcom.py

@@ -0,0 +1,23 @@
+class Solution:
+    def setZeroes(self, matrix):
+        first_row_zero = any(matrix[0][j] == 0 for j in range(len(matrix[0])))
+        first_col_zero = any(matrix[i][0] == 0 for i in range(len(matrix)))
+
+        for i in range(1, len(matrix)):
+            for j in range(1, len(matrix[0])):
+                if matrix[i][j] == 0:
+                    matrix[i][0] = 0
+                    matrix[0][j] = 0
+
+        for i in range(1, len(matrix)):
+            for j in range(1, len(matrix[0])):
+                if matrix[i][0] == 0 or matrix[0][j] == 0:
+                    matrix[i][j] = 0
+
+        if first_row_zero:
+            for j in range(len(matrix[0])):
+                matrix[0][j] = 0
+
+        if first_col_zero:
+            for i in range(len(matrix)):
+                matrix[i][0] = 0

unique-paths/printjin-gmailcom.py

@@ -0,0 +1,7 @@
+class Solution:
+    def uniquePaths(self, m, n):
+        dp = [[1] * n for _ in range(m)]
+        for i in range(1, m):
+            for j in range(1, n):
+                dp[i][j] = dp[i - 1][j] + dp[i][j - 1]
+        return dp[m - 1][n - 1]