题解 | #字符个数统计#

const rl = require("readline").createInterface({ input: process.stdin });
const set = new Set()
rl.on('line', (line) => {
  while (line.length) {
    const c = line.substring(0, 1)
    line = line.substring(1)
    const ascii = c.charCodeAt()
    ascii >=0 && ascii <= 127 && set.add(c)
  }

  console.log(set.size)
})