Update 0322-coin-change.kt

Author: a93a

kotlin/0322-coin-change.kt

@@ -1,14 +1,42 @@
+// DP
 class Solution {
     fun coinChange(coins: IntArray, amount: Int): Int {
-        val dp = IntArray(amount+1){amount+1}
+        val dp = IntArray (amount + 1) { amount + 1 }
         dp[0] = 0
-        for(i in 0 .. amount){
-            for (j in 0 until coins.size){
-                if(coins[j]<=i){
-                    dp[i] = minOf(dp[i], dp[i-coins[j]]+1)
+        for (i in 0..amount) {
+            for (j in 0 until coins.size) {
+                if (coins[j] <= i) {
+                    dp[i] = minOf(dp[i], dp[i - coins[j]] + 1)
                 }
             }
         }
-        return if(dp[amount]>amount) -1 else dp[amount]
+        return if (dp[amount] > amount) -1 else dp[amount]
     }
-}
+}
+
+// Recursion + memoization
+class Solution {
+    fun coinChange(coins: IntArray, amount: Int): Int {
+        val dp = IntArray (amount + 1) { -1 }
+
+        fun dfs(amount: Int): Int {
+            if (amount == 0) return 0
+            if (dp[amount] != -1) return dp[amount]
+
+            var res = Integer.MAX_VALUE
+            for (coin in coins) {
+                if (amount - coin >= 0) {
+                    var count = dfs(amount - coin)
+                    if (count != Integer.MAX_VALUE)
+                        res = minOf(res, count + 1)
+                }
+            }
+
+            dp[amount] = res
+            return res
+        }
+
+        val res = dfs(amount)
+        return if (res == Integer.MAX_VALUE) -1 else res
+    }
+}