Minimum Number of Days to Eat N Oranges.cpp

/*
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.

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.

Example 3:
  Input: n = 1
  Output: 1

Example 4:
  Input: n = 56
  Output: 6
 

Constraints:
  1 <= n <= 2*10^9

*/
class Solution {
    unordered_map<int, int> dp;
public:
    int minDays(int n) {
        if (n <= 1)
            return n;
        if (dp.count(n) == 0)
            dp[n] = 1 + min(n % 2 + minDays(n / 2), n % 3 + minDays(n / 3));
        return dp[n];
    }
};