src/bin/coin-change.rs

Author: bestgopher

src/bin/coin-change.rs

@@ -0,0 +1,49 @@
+fn main() {
+    println!("{}", Solution::coin_change(vec![1, 2, 5], 11));
+    println!("{}", Solution::coin_change(vec![1], 1));
+    println!("{}", Solution::coin_change(vec![1, 2, 5], 100));
+}
+
+struct Solution;
+
+impl Solution {
+    pub fn coin_change(coins: Vec<i32>, amount: i32) -> i32 {
+        if amount == 0 { return 0; }
+
+        let mut h = std::collections::HashMap::new();
+
+        Self::f(&coins[..], &mut h, amount)
+    }
+
+    fn f(coins: &[i32], h: &mut std::collections::HashMap<i32, i32>, amount: i32) -> i32 {
+        let mut num = -1;
+
+        for &i in coins {
+            if i > amount {
+                continue;
+            } else if i == amount {
+                return 1;
+            }
+
+            let x = if let Some(x) = h.get(&(amount - i)) {
+                *x
+            } else {
+                Self::f(coins, h, amount - i)
+            };
+
+            if x == -1 {
+                continue;
+            }
+
+            if num == -1 {
+                num = x + 1;
+            } else {
+                num = num.min(x + 1);
+            }
+        }
+
+        h.insert(amount, num);
+
+        num
+    }
+}