Check if it is possible to get back to 12 O-clock only by adding or subtracting given seconds in Python

Suppose we have an array of n different second values. We have to check whether it is possible to start from 12'O clock and go back to 12 by only adding or subtracting the given seconds or not. We can use all given seconds exactly once, we can either add seconds or subtract it.

So, if the input is like seconds = [40,90,50], then the output will be True as it can add 40 then subtract 90 then again add 50.

To solve this, we will follow these steps −

• size := 2^(length of seconds array)
• for c in range 0 to size - 1, do
  • add := 0
  • for j in range 0 to size of seconds - 1, do
    • if c AND (2^j) is non-zero, then
      • add := add + seconds[j]
    • otherwise,
      • add := add - seconds[j]
  • if add is divisible by (24 * 60), then
    • return True
• return False

Example

Let us see the following implementation to get better understanding −

 Live Demo

def solve(seconds):
   size = 2**len(seconds)
   for c in range(size):
      add = 0
      for j in range(len(seconds)) :
         if c & (1 << j):
            add += seconds[j]
         else:
            add -= seconds[j]
      if add % (24 * 60) == 0:
         return True
   return False
seconds = [40,90,50]
print(solve(seconds))

Input

[40,90,50]

Output

True

Arnab Chakraborty

Updated on: 18-Jan-2021

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