题解 | 字符个数统计

使用哈希，没有就加入哈希表，有就不用操作，最后输出哈希表长度

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
    const line = await readline()
    const hashMap = new Map()
    for(const char of line){
        if(!hashMap.has(char)) hashMap.set(char,1)
    }
    console.log(hashMap.size)
}()