题解 | #圣诞树#

const list = [];
function push(num) {
    if(!isLegal(num)) {
        return;
    }
    list.unshift(parseInt(num))
}
function pop() {
    if(list.length<=0) {
        console.log('error')
        return;
    }
    const num = list.shift()
    console.log(num)
    return num
}
function top() {
    if(list.length<=0) {
        console.log('error')
        return
    }
    const num= list[0];
    console.log(num)
    return num
}
function isLegal(str) {
    if(!/\d+/.test(str)){
        console.log('str should be a integar number')
        return false;
    }
    let num = parseInt(str);
    if(num <1 || num > 100000) {
        console.log('num should be between 1 and 100000')
        return false;
    }
    return true;
}

const readline = require('readline'); const r1= readline.createInterface({ input:process.stdin, output:process.stdout }) r1.on('line',(data) => { if(/push \d+/.test(data)) { let str = /push (\d+)/.exec(data)[1] push(str) } else if(/pop/.test(data)){ pop(); } else if(/top/.test(data)) { top(); } });