LC 1716

Math
Math
Publish Date:   2022-07-01

Solution to LeetCode 1716 Calculate Money in Leetcode Bank.

LeetCode 1716

Calculate Money in Leetcode Bank (Easy). [link]

1] Math. Time complexity O(N). Space complexity O(1).

class Solution(object):
    def totalMoney(self, n):
        """
        :type n: int
        :rtype: int
        """
        week, day = 0, 1
        res = 0
        for i in range(n):
            res += week + day 
            day += 1
            if day == 8:
                day = 1
                week += 1
        return res

2] Arithmetic progression. For each week, the money increases by 7. Sum up the money for the full weeks and the money for the remaining days. Time complexity O(1). Space complexity O(1).

class Solution(object):
    def totalMoney(self, n):
        """
        :type n: int
        :rtype: int
        """
        # for entire weeks
        weekNum = n // 7
        firstWeek = (1 + 7) * 7 // 2 # money in the first week
        lastWeek = firstWeek + 7 * (weekNum - 1) # money in the last week
        allWeeks = (firstWeek + lastWeek) * weekNum // 2 # sum all money
        
        # for remaining days
        dayNum = n % 7
        firstDay = 1 + weekNum # money in the first day of the remaining days
        lastDay = firstDay + dayNum - 1 # money in the last day of the remaining days
        allDays = (firstDay + lastDay) * dayNum // 2 # sum all money
        return allWeeks + allDays
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