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by Sumit Chourasia | Jan 10, 2021 | Category :coding | Tags : algorithm data-structure easy leetcode maths

Calculate Money in Leetcode Bank - Maths - Easy - LeetCode

Calculate Money in Leetcode Bank - Maths - Easy - LeetCode

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

public class Solution {
    public int TotalMoney(int n) {
        int extra = n%7;
        int weeks = n/7;
        int sum = 28 * weeks + 7 * (weeks)*(weeks-1)/2 + weeks*extra + (extra)*(extra+1)/2;
        return sum;
    }
}

Time Complexity: O(1)

Space Complexity: O(1)

Contributed By: Sumit Chourasia
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