Given a string, sort it in decreasing order based on the frequency of characters.

Example 1:

Input:
"tree"

Output:
"eert"

Explanation:
‘e‘ appears twice while ‘r‘ and ‘t‘ both appear once.
So ‘e‘ must appear before both ‘r‘ and ‘t‘. Therefore "eetr" is also a valid answer.

Example 2:

Input:
"cccaaa"

Output:
 

"cccaaa"

Explanation:
Both ‘c‘ and ‘a‘ appear three times, so "aaaccc" is also a valid answer.
Note that "cacaca" is incorrect, as the same characters must be together.

Example 3:

Input:
"Aabb"

Output:
"bbAa"

Explanation:
"bbaA" is also a valid answer, but "Aabb" is incorrect.
Note that ‘A‘ and ‘a‘ are treated as two different characters.

/**
 * @param {string} s
 * @return {string}
 */
var frequencySort = function (s) {
    let m = {};
    for (let i in s) {
        let c = s[i];
        if (m[c]) {
            m[c]++;
        } else {
            m[c] = 1;
        }
    }
    let arr = [];
    for (let i in m) {
        let d = 
 
{};
        d.str = i;
        d.time = m[i];
        arr.push(d);
    }
    arr.sort((a, b) => {
        return b.time - a.time;
    });
    let res = "";
    for (let i in arr) {
        let item = arr[i];
        res += item.str.repeat(item.time);
    }
    return res;
};
// let s = "Aabb";
// console.log(frequencySort(s));

451. Sort Characters By Frequency 按頻率排序字符