We are playing the Guessing Game. The game will work as follows:
- I pick a number between
1andn. - You guess a number.
- If you guess the right number, you win the game.
- If you guess the wrong number, then I will tell you whether the number I picked is higher or lower, and you will continue guessing.
- Every time you guess a wrong number
x, you will payxdollars. If you run out of money, you lose the game.
Given a particular n, return the minimum amount of money you need to guarantee a win regardless of what number I pick.
Example 1:
Input: n = 10 Output: 16 Explanation: The winning strategy is as follows: - The range is [1,10]. Guess 7. - If this is my number, your total is $0. Otherwise, you pay $7. - If my number is higher, the range is [8,10]. Guess 9. - If this is my number, your total is $7. Otherwise, you pay $9. - If my number is higher, it must be 10. Guess 10. Your total is $7 + $9 = $16. - If my number is lower, it must be 8. Guess 8. Your total is $7 + $9 = $16. - If my number is lower, the range is [1,6]. Guess 3. - If this is my number, your total is $7. Otherwise, you pay $3. - If my number is higher, the range is [4,6]. Guess 5. - If this is my number, your total is $7 + $3 = $10. Otherwise, you pay $5. - If my number is higher, it must be 6. Guess 6. Your total is $7 + $3 + $5 = $15. - If my number is lower, it must be 4. Guess 4. Your total is $7 + $3 + $5 = $15. - If my number is lower, the range is [1,2]. Guess 1. - If this is my number, your total is $7 + $3 = $10. Otherwise, you pay $1. - If my number is higher, it must be 2. Guess 2. Your total is $7 + $3 + $1 = $11. The worst case in all these scenarios is that you pay $16. Hence, you only need $16 to guarantee a win.
Example 2:
Input: n = 1 Output: 0 Explanation: There is only one possible number, so you can guess 1 and not have to pay anything.
Example 3:
Input: n = 2 Output: 1 Explanation: There are two possible numbers, 1 and 2. - Guess 1. - If this is my number, your total is $0. Otherwise, you pay $1. - If my number is higher, it must be 2. Guess 2. Your total is $1. The worst case is that you pay $1.
Constraints:
1 <= n <= 200
struct Solution;
use std::collections::HashMap;
impl Solution {
fn get_money_amount(n: i32) -> i32 {
let mut memo: HashMap<(i32, i32), i32> = HashMap::new();
Self::dp(1, n, &mut memo)
}
fn dp(left: i32, right: i32, memo: &mut HashMap<(i32, i32), i32>) -> i32 {
if left == right {
0
} else {
if let Some(&res) = memo.get(&(left, right)) {
return res;
}
let mut res = std::i32::MAX;
for i in left..right {
let a = if i != left {
Self::dp(left, i - 1, memo)
} else {
0
};
let b = if i != right {
Self::dp(i + 1, right, memo)
} else {
0
};
res = res.min(i + a.max(b));
}
memo.insert((left, right), res);
res
}
}
}
#[test]
fn test() {
let n = 10;
let res = 16;
assert_eq!(Solution::get_money_amount(n), res);
}