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 () {
    // 切割字符串，利用set去重，然后转数组，输出字符串长度
    while(line = await readline()){
        let tokens = line.split('');
        tokens = Array.from(new Set(tokens));
        console.log(tokens.length);
    }
}()