题解 | #字符个数统计#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    // Write your code here
    while(line = await readline()){
		/*这里新建一个set对象，利用set特性自动去除重复字符*/
        let set = new Set()
        for(let i=0;i<line.length;i++){
            set.add(line[i]);
        }
		/*.size获取长度*/
        console.log(set.size)
    }
}()