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 () {
    while(line = await readline()) {
		// 用map存储不同的字母
        let map = new Map()
        let count = 0
        for(let i = 0;i < line.length;i++) {
            if (!map.get(line[i])) {
                map.set(line[i],1)
                count++
            }
        }
        console.log(count)
    }
}()