add: 377

Author: huyjs9

README.md

@@ -17,6 +17,7 @@
 | 221  | [Maximal Square](./src/221.maximal-square.py)                                                                              | Medium | O(R\*C)      | O(1)       | Array, Dynamic Programming, Matrix                                  | DP (Min - Max)                |
 | 279  | [Perfect Squares](./src/279.perfect-squares.py)                                                                            | Medium | O(N\*log(N)) | O(N)       | Math, Dynamic Programming, BFS                                      | DP (Min - Max)                |
 | 322  | [Coin Change](./src/322.coin-change.py)                                                                                    | Medium | O(A\*N)      | O(A)       | Array, Dynamic Programming, Breadth-First Search                    | DP (Min - Max)                |
+| 377  | [Combination Sum IV](./src/377.combination-sum-iv.py)                                                                      | Medium | O(N\*T)      | O(T)       | Array, Dynamic Programming                                          | DP (Distinct Ways)            |
 | 474  | [Ones And Zeros](./src/474.ones-and-zeros.py)                                                                              | Medium | O(M\*N\*L)   | O(M\*N\*L) | Array, String, Dynamic Programming                                  | DP (Min - Max)                |
 | 494  | [Target Sum](./src/494.target-sum.py)                                                                                      | Medium | O(N\*T)      | O(T)       | Dynamic Programming                                                 | DP (Distinct Ways)            |
 | 650  | [2 Keys Keyboard](./src/650.2-keys-keyboard.py)                                                                            | Medium | O(N)         | O(N)       | Math, Dynamic Programming                                           | DP (Min - Max)                |

src/377.combination-sum-iv.py

@@ -0,0 +1,58 @@
+# Level: Medium
+# TAGS: Array, Dynamic Programming
+
+from typing import List
+
+
+class Solution:
+    # DP Bottom-Up | Time: O(N*T) | Space: O(T)
+    def combinationSum4(self, nums: List[int], target: int) -> int:
+        n = len(nums)
+        memo = {}
+
+        def dfs(t):
+            if t == 0:
+                return 1
+            if t < 0:
+                return 0
+            if t in memo:
+                return memo[t]
+            res = 0
+            for j in range(n):
+                res += dfs(t - nums[j])
+
+            memo[t] = res
+            return memo[t]
+
+        return dfs(target)
+
+    # DP Top-Down | Time: O(N*T) | Space: O(T)
+    def combinationSum4_1(self, nums: List[int], target: int) -> int:
+        n = len(nums)
+        dp = [0] * (target + 1)
+        dp[0] = 1
+
+        for i in range(1, target + 1):
+            for j in range(n):
+                if i - nums[j] >= 0:
+                    dp[i] += dp[i - nums[j]]
+
+        return dp[target]
+
+
+tests = [
+    (
+        (
+            [1, 2, 3],
+            4,
+        ),
+        7,
+    ),
+    (
+        (
+            [9],
+            3,
+        ),
+        0,
+    ),
+]