1553. Minimum Number of Days to Eat N Oranges: AC

Author: tan-wei

src/solution/mod.rs

@@ -1171,3 +1171,4 @@ mod s1547_minimum_cost_to_cut_a_stick;
 mod s1550_three_consecutive_odds;
 mod s1551_minimum_operations_to_make_array_equal;
 mod s1552_magnetic_force_between_two_balls;
+mod s1553_minimum_number_of_days_to_eat_n_oranges;

src/solution/s1553_minimum_number_of_days_to_eat_n_oranges.rs

@@ -0,0 +1,92 @@
+/**
+ * [1553] Minimum Number of Days to Eat N Oranges
+ *
+ * There are n oranges in the kitchen and you decided to eat some of these oranges every day as follows:
+ *
+ * 	Eat one orange.
+ * 	If the number of remaining oranges n is divisible by 2 then you can eat n / 2 oranges.
+ * 	If the number of remaining oranges n is divisible by 3 then you can eat 2 * (n / 3) oranges.
+ *
+ * You can only choose one of the actions per day.
+ * Given the integer n, return the minimum number of days to eat n oranges.
+ *  
+ * Example 1:
+ *
+ * Input: n = 10
+ * Output: 4
+ * Explanation: You have 10 oranges.
+ * Day 1: Eat 1 orange,  10 - 1 = 9.  
+ * Day 2: Eat 6 oranges, 9 - 2*(9/3) = 9 - 6 = 3. (Since 9 is divisible by 3)
+ * Day 3: Eat 2 oranges, 3 - 2*(3/3) = 3 - 2 = 1.
+ * Day 4: Eat the last orange  1 - 1  = 0.
+ * You need at least 4 days to eat the 10 oranges.
+ *
+ * Example 2:
+ *
+ * Input: n = 6
+ * Output: 3
+ * Explanation: You have 6 oranges.
+ * Day 1: Eat 3 oranges, 6 - 6/2 = 6 - 3 = 3. (Since 6 is divisible by 2).
+ * Day 2: Eat 2 oranges, 3 - 2*(3/3) = 3 - 2 = 1. (Since 3 is divisible by 3)
+ * Day 3: Eat the last orange  1 - 1  = 0.
+ * You need at least 3 days to eat the 6 oranges.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= n <= 2 * 10^9
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/minimum-number-of-days-to-eat-n-oranges/
+// discuss: https://leetcode.com/problems/minimum-number-of-days-to-eat-n-oranges/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn min_days(n: i32) -> i32 {
+        let mut dp = std::collections::HashMap::new();
+
+        Self::dfs_helper(n, &mut dp)
+    }
+
+    fn dfs_helper(n: i32, dp: &mut std::collections::HashMap<i32, i32>) -> i32 {
+        if n <= 1 {
+            return n;
+        }
+
+        if !dp.contains_key(&n) {
+            let a = n % 2 + Self::dfs_helper(n / 2, dp);
+            let b = n % 3 + Self::dfs_helper(n / 3, dp);
+            dp.insert(n, 1 + a.min(b));
+        }
+
+        *dp.get(&n).unwrap()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1553_example_1() {
+        let n = 10;
+
+        let result = 4;
+
+        assert_eq!(Solution::min_days(n), result);
+    }
+
+    #[test]
+    fn test_1553_example_2() {
+        let n = 6;
+
+        let result = 3;
+
+        assert_eq!(Solution::min_days(n), result);
+    }
+}