leetcode-1716-easy

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

思路一：统计有多少周，再统计剩余不足一周的天数。还有一种思路是直接用数学公式

public int totalMoney(int n) {
	int x = n / 7;
	int y = n % 7;

	int sum = 0;
	int i = 0;
	for (; i < x; i++) {
		sum += 28;
		sum += i*7;
	}

	int val = x + 1 ;
	for (int j = 0; j < y; j++) {
		sum += val++;
	}

	return sum;
}