leet/basic-calculator.js at master · coderpawz/leet · GitHub

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/**
 * @param {string} s
 * @return {number}
 */
const calculate = function(s) {
  const stack = [];
  let number = 0;
  let sign = 1;
  let result = 0;
  for (var ii = 0; ii < s.length; ii++) {
    const ch = s.charAt(ii);
    switch (ch) {
    case ' ':
      continue;
    case '+':
      result += sign * number;
      number = '';
      sign = 1;
      break;
    case '-':
      result += sign * number;
      number = 0;
      sign = -1;
      break;
    case ')':
      result += sign * number;
      result *= stack.pop();
      result += stack.pop();
      number = '';
      break;
    case '(':
      stack.push(result);
      stack.push(sign);
      result = 0;
      sign = 1;
      break;
    default:
      number = number * 10 + parseInt(ch);
      break;
    }
  }
  if (number) {
    result += sign * number;
  }
  return result;
};

console.log(2, calculate('1 + 1'));
console.log(0, calculate('0 + 1 -1'));
console.log(-12, calculate('1-11+0-2'));
console.log(3, calculate(' 2-1 + 2'));
console.log(23, calculate('(1+(4+5+2)-3)+(6+8)'));
console.log(123242442, calculate('123242442'));