new recursion code

Author: ankurbhambri

array/calendar.py

@@ -1,3 +1,4 @@
+from typing import List
 from sortedcontainers import SortedDict
 
 # https://leetcode.com/problems/my-calendar-i/
@@ -108,3 +109,19 @@ def book(self, start: int, end: int) -> bool:
 # similar problems:
 # https://leetcode.com/problems/car-pooling/
 # https://leetcode.com/problems/corporate-flight-bookings/submissions/
+
+
+# https://leetcode.com/problems/corporate-flight-bookings/
+class Solution:
+    def corpFlightBookings(self, bookings: List[List[int]], n: int) -> List[int]:
+
+        hm = [0] * (n + 1)
+
+        for i, j, v in bookings:
+            hm[i - 1] += v
+            hm[j] -= v
+
+        for i in range(1, n):
+            hm[i] += hm[i - 1]
+
+        return hm[:-1]

binary_search/3sumCloset.py

@@ -0,0 +1,33 @@
+def letterCombinations(digits):
+
+    res = []
+
+    hm = {
+        "2": "abc",
+        "3": "def",
+        "4": "ghi",
+        "5": "jkl",
+        "6": "mno",
+        "7": "pqrs",
+        "8": "tuv",
+        "9": "wxyz",
+    }
+
+    def dfs(i, curr):
+
+        if len(curr) == len(digits):
+            res.append(curr)
+            return
+
+        for c in hm[digits[i]]:
+            dfs(i + 1, curr + c)
+
+    if digits:
+        dfs(0, "")
+    return res
+
+
+print(letterCombinations("23"))
+print(letterCombinations("234"))
+print(letterCombinations("2345"))
+print(letterCombinations("23456"))

recursion/letter_combinations.py

@@ -0,0 +1,36 @@
+# https://leetcode.com/problems/regular-expression-matching/
+
+
+def isMatch(s, p):
+
+    memo = {}
+
+    def helper(i, j):
+
+        if j >= len(p):
+            return i >= len(s)
+
+        if (i, j) in memo:
+            return memo[(i, j)]
+
+        first_char = i < len(s) and (p[j] == s[i] or p[j] == ".")
+
+        if j + 1 < len(p) and p[j + 1] == "*":
+
+            notTake = helper(i, j + 2)
+            take = first_char and helper(i + 1, j)
+
+            memo[(i, j)] = notTake or take
+
+            return memo[(i, j)]
+
+        memo[(i, j)] = first_char and helper(i + 1, j + 1)
+
+        return memo[(i, j)]
+
+    return helper(0, 0)
+
+
+print(isMatch("aa", "a"))  # False
+print(isMatch("aa", "a*"))  # True
+print(isMatch("ab", ".*"))  # True