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 按频率排序字符
原文：http://www.cnblogs.com/xiejunzhao/p/7679664.html