solved coin-change.

Author: sangbeenmoon

coin-change/sangbeenmoon.py

@@ -0,0 +1,32 @@
+# dp[i] = min(dp[i - c0], dp[i - c1], ... , dp[i - cn]) + 1
+
+# TC : O(amount * len(coins))
+# SC : O(amount)
+
+class Solution:
+    dp = []
+    def coinChange(self, coins: List[int], amount: int) -> int:
+        self.dp = [-2] * (amount + 10)  # 아직 방문하지 않음 -> -2
+        
+        return self.go(amount, coins)
+        
+        
+    def go(self, x: int, coins: List[int]) -> int:
+        if x == 0:
+            return 0
+
+        if self.dp[x] != -2:
+            return self.dp[x]
+        
+        mm = 100000
+
+        for coin in coins:
+            if x - coin >= 0:
+                sub = self.go(x - coin, coins)
+                if (sub == -1): # 불가능 -> -1
+                    continue
+                mm = min(mm, sub + 1)
+        
+        self.dp[x] = mm if mm != 100000 else -1 # memoization
+            
+        return self.dp[x]