Different Ways to Add Parentheses

Description

Given a string of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. The valid operators are +, - and *.

Example 1:

Input: "2-1-1"
Output: [0, 2]
Explanation: 
((2-1)-1) = 0 
(2-(1-1)) = 2

Example 2:

Input: "2*3-4*5"
Output: [-34, -14, -10, -10, 10]
Explanation: 
(2*(3-(4*5))) = -34 
((2*3)-(4*5)) = -14 
((2*(3-4))*5) = -10 
(2*((3-4)*5)) = -10 
(((2*3)-4)*5) = 10

Solution(javascript)

const memo = {}
const diffWaysToCompute = (input = '') => {
  if (memo[input] !== undefined) {
    return memo[input]
  }
  const result = []
  if (input.length === 1) {
    return [parseInt(input, 10)]
  }
  for (let i = 0; i < input.length; i++) {
    if (
      input[i] === '-'
        || input[i] === '+'
        || input[i] === '*'
    ) {
      const leftParts = diffWaysToCompute(input.substring(0, i))
      const rightParts = diffWaysToCompute(input.substring(i + 1))
      for (const left of leftParts) {
        for (const right of rightParts) {
          switch (input[i]) {
            case '-':
              result.push(left - right)
              break
            case '+':
              result.push(left + right)
              break
            case '*':
              result.push(left * right)
              break
            default:
              break
          }
        }
      }
    }
  }
  memo[input] = result.length === 0 && input.length > 0 ? [parseInt(input, 10)] : result
  return memo[input]
}