题解 | 最小循环节

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
	//经分析，为去重后的数组长度
    while ((line = await readline())) {
        let tokens = line.split("");

        const arr = new Set(tokens);
        const _arr = Array.from(arr);
        console.log(_arr.length)
        return _arr.length;
    }
})();