coin change 2

Author: jhideki

src/coin_change2.rs

@@ -0,0 +1,32 @@
+use std::collections::HashMap;
+pub struct Solution {}
+impl Solution {
+    pub fn change(amount: i32, coins: Vec<i32>) -> i32 {
+        let mut mem: HashMap<(usize, i32), i32> = HashMap::new();
+        Self::dfs(0, 0, amount, &coins, &mut mem)
+    }
+
+    fn dfs(
+        sum: i32,
+        i: usize,
+        amount: i32,
+        coins: &Vec<i32>,
+        mem: &mut HashMap<(usize, i32), i32>,
+    ) -> i32 {
+        if sum > amount || i >= coins.len() {
+            return 0;
+        }
+
+        if sum == amount {
+            return 1;
+        }
+
+        if let Some(val) = mem.get(&(i, sum)) {
+            return *val;
+        }
+        let val = Self::dfs(sum + coins[i], i, amount, coins, mem)
+            + Self::dfs(sum, i + 1, amount, coins, mem);
+        mem.insert((i, sum), val);
+        val
+    }
+}

src/main.rs

@@ -1,2 +1,2 @@
-mod best_time_stock_cooldown;
+mod coin_change2;
 fn main() {}