Given a perimeter P, the task is to find the number of right triangles possible with perimeter equal to p.
Input: P = 12 Output: number of right triangles = 1 The only right angle possible is with sides hypotenuse = 5, perpendicular = 4 and base = 3. Input: p = 840 Output: number of right triangles = 8
So the aim is to find the number of solutions which satisfy equations a + b + c = p and a2 + b2 = c2.
A naive approach is to run two loops for a(1 to p/2) and b(a+1 to p/3) then make c=p-a-b and increase count by one if . This will take time.
An efficient approach can be found by little algebraic manipulation :
Since a + c > b or, p – b > b or, b < p/2. Thus iterating b from 1 to p/2, calculating a and storing only the whole number a would give all solutions for a given p. There are no right triangles are possible for odd p as right angle triangles follow the Pythagoras theorem. Use a list of pairs to store the values of a and band return the count at the end.
Below is the implementation of the above approach.
number of right triangles = 8
Time complexity: O(P)