150-Evaluate-Reverse-Polish-Notation.ts

function evalRPN(tokens: string[]): number {
    const stack: number[] = [];

    tokens.forEach((token) => {
        if (token === '+') {
            stack.push(Number(stack.pop()) + Number(stack.pop()));
        } else if (token === '-') {
            const a = Number(stack.pop());
            const b = Number(stack.pop());
            stack.push(b - a);
        } else if (token === '/') {
            const a = Number(stack.pop());
            const b = Number(stack.pop());
            stack.push(Math.trunc(b / a));
        } else if (token === '*') {
            stack.push(Number(stack.pop()) * Number(stack.pop()));
        } else {
            stack.push(Number(token));
        }
    });

    return stack[0];
}