题解

function removeKdigits(num: string, k: number): string {
    if (k <= 0) return num;
    let saveLen = num.length - k;
    let stack = [];
    for (let i = 0; i < num.length; i++) {
        while (k && stack.length && stack[stack.length - 1] > num.charAt(i)) {
            stack.pop();
            k--;
        }
        stack.push(num.charAt(i));
    }
    let res = stack.splice(0, saveLen);
    console.log(res);
    while (res && res[0] === '0') {
        res.shift();
    }
    return res.join('') || '0';
};