README.md

1716. Calculate Money in Leetcode Bank

Hercy wants to save money for his first car. He puts money in the Leetcode bank every day.

He starts by putting in $1 on Monday, the first day. Every day from Tuesday to Sunday, he will put in $1 more than the day before. On every subsequent Monday, he will put in $1 more than the previous Monday.

Given n, return the total amount of money he will have in the Leetcode bank at the end of the nth day.

Example 1:

Input: n = 4
Output: 10
Explanation: After the 4th day, the total is 1 + 2 + 3 + 4 = 10.

Example 2:

Input: n = 10
Output: 37
Explanation: After the 10th day, the total is (1 + 2 + 3 + 4 + 5 + 6 + 7) + (2 + 3 + 4) = 37. Notice that on the 2nd Monday, Hercy only puts in $2.

Example 3:

Input: n = 20
Output: 96
Explanation: After the 20th day, the total is (1 + 2 + 3 + 4 + 5 + 6 + 7) + (2 + 3 + 4 + 5 + 6 + 7 + 8) + (3 + 4 + 5 + 6 + 7 + 8) = 96.

Constraints:

• 1 <= n <= 1000

Solutions (Ruby)

1. Mathematical

# @param {Integer} n
# @return {Integer}
def total_money(n)
  x = n / 7
  y = n % 7

  28 * x + x * (x - 1) * 7 / 2 + (x + 1) * y + y * (y - 1) / 2
end

Solutions (Rust)

1. Mathematical

impl Solution {
    pub fn total_money(n: i32) -> i32 {
        let x = n / 7;
        let y = n % 7;

        28 * x + x * (x - 1) * 7 / 2 + (x + 1) * y + y * (y - 1) / 2
    }
}