题解 | #挑7#

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())) {
        const n = parseInt(line);
        let number = 0;
        for (let i = 1; i <= n; i++) {
            if (i % 7 === 0) number++;
            else{
                var item = i.toString();
                for(const j of item) {
                    if(j==='7'){
                        number++;
                        break;
                    }
                }
            }
        }
        console.log(number);
    }
})();

两种情况：

1. 7的倍数
2. 该数字转化为的字符串包含字符‘7’