parse-bool-expr.js

/// https://leetcode.com/problems/parsing-a-boolean-expression

/**
 * @param {string} expression
 * @return {boolean}
 */
var parseBoolExpr = function(expression) {
  const stack = [];
  for (let i = 0; i <= expression.length; ++i) {
    const c = expression[i];
    if (c === '(' || c === ',') continue;
    if (c === '!') stack.push(not);
    else if (c === '&') stack.push(and);
    else if (c === '|') stack.push(or);
    else if (c === 't') stack.push(true);
    else if (c === 'f') stack.push(false);
    else if (c === ')') {
      const params = [];
      while (typeof stack[stack.length - 1] === 'boolean') {
        params.push(stack.pop());
      }
      const func = stack.pop();
      stack.push(func(params));
    }
  }
  return stack[stack.length - 1];
};

const not = xs => !xs[0];
const or = xs => xs.some(x => x);
const and = xs => xs.every(x => x);