1
/**
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 * @param {string} expression
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 * @return {number}
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 */
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var evaluate = function (expression) {
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  return helper(expression);
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};
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const helper = (expr, map = {}) => {
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  if (expr[0] !== "(") return /[0-9]|-/.test(expr[0]) ? +expr : map[expr];
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  map = Object.assign({}, map);
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  const start = expr[1] === "m" ? 6 : 5;
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  const tokens = parse(expr.slice(start, expr.length - 1));
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  if (expr.startsWith("(m"))
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    return helper(tokens[0], map) * helper(tokens[1], map);
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  if (expr.startsWith("(a"))
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    return helper(tokens[0], map) + helper(tokens[1], map);
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  for (let i = 0; i < tokens.length - 2; i += 2)
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    map[tokens[i]] = helper(tokens[i + 1], map);
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  return helper(tokens.at(-1), map);
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};
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const parse = (expr) => {
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  const tokens = [];
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  let [builder, par] = ["", 0];
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  for (let ch of expr) {
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    if (ch === "(") par++;
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    if (ch === ")") par--;
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    if (!par && ch === " ") {
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      tokens.push(builder);
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      builder = "";
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    } else builder += ch;
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  }
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  return builder ? [...tokens, builder] : tokens;
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};