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 () {
    // Write your code here
    while ((line = await readline())) {
        let diff = [];
        for (const j of line) {
            if (diff.some((item) => item === j)) continue;
            else diff.push(j);
        }
        console.log(diff.length);
    }
})();

如果在diff数组中找到了目前的元素，就跳过，

否则，将目前元素push进diff数组中