Find Position of First Even Number in Triangle of Numbers in Python

Suppose we are generating a number triangle like below

      1
    1 1 1
  1 2 3 2 1
1 3 6 7 6 3 1

where in each row the elements are generated by adding three numbers on top of it. Now if we have a line number l. We have to find the position of first even number of that line. The position values are starting from 1.

So, if the input is like l = 5, then the output will be 2

           1
        1  1  1
     1  2  3  2  1
  1  3  6  7  6  3 1
1 4 10 16 19 16 10 4 1

To solve this, we will follow these steps −

• if l is same as 1 or l is same as 2, then
  • return -1
• otherwise when l mod 2 is same as 0, then
  • if l mod 4 is same as 0, then
    • return 3
  • otherwise,
    • return 4
• otherwise,
  • return 2

Example

Let us see the following implementation to get better understanding −

def solve(l):
   if l == 1 or l == 2 :
      return -1
   elif l % 2 == 0:
      if l % 4 == 0:
         return 3
      else:
         return 4
   else:
      return 2

l = 5
print(solve(l))

Input

5

Output

2