Evaluating Simple Algebra

Challenge Difficulty: Medium | Estimated completion time: ~20 minutes

Given a string containing an algebraic equation, calculate and return the value of x.

You’ll only be given equations for simple addition and subtraction.

Examples

evalAlgebra("2 + x = 19")
output = 17
 
evalAlgebra("4 - x = 1")
output = 3
 
evalAlgebra("x + 10 = 53")
output = 43
 
evalAlgebra("-23 + x = -20")
output = 3
 
evalAlgebra("10 + x = 5")
output = -5
 
evalAlgebra("-49 - x = -180")
output = 131
 
evalAlgebra("x - 22 = -56")
output = -34

Solution

Python

def eval_algebra(equation: str) -> int: """Solve a simple algebraic equation for x. Args: equation: String equation with x, +, -, and = Returns: Value of x """ left, right = equation.split(" = ") result = int(right) parts = left.replace("- ", "-").replace("+ ", "+").split() for part in parts: if part == "x": continue elif "x" in part: coefficient = part.replace("x", "") if coefficient <span class="text-highlight"> "" or coefficient </span> "+": continue elif coefficient == "-": result += 1 else: result -= int(coefficient) else: if part.startswith("+"): result -= int(part[1:]) else: result -= int(part) if left.startswith("x"): return result elif left.endswith("x"): return result elif " x " in left: return result return result if __name__ == "__main__": print(eval_algebra("2 + x = 19")) # 17 print(eval_algebra("4 - x = 1")) # 3 print(eval_algebra("x + 10 = 53")) # 43 print(eval_algebra("-23 + x = -20")) # 3

Output