题解 | 字符个数统计

const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});
rl.on('line', function (line) {
    const map = {}
    const arr = line.split('')
    let count = 0
    for (let x of arr) {
        if (!map[x]) {
            map[x] = 1
            count++
        }
    }
    console.log(count)
});