题解 | #字符统计#

let str = readline();
let arr = [...new Set(str.split(''))];
let brr = [];
let obj = {};
let s = '';
for(let i = 0; i < str.length; i++) {
    let n = str[i];
    if(obj[n]) {
        obj[n] += 1;
    } else {
        obj[n] = 1;
    }
}
for(let i = 0; i < arr.length; i++) {
    brr.push({
        n: arr[i],
        num: obj[arr[i]]
    });
}
brr.sort((a, b) => {
    if(a.num == b.num) {
        return a.n.charCodeAt(0) - b.n.charCodeAt(0);
    }
    return b.num - a.num;
});
for(let i = 0; i < brr.length; i++) {
    s += brr[i].n;
}
console.log(s);