LeetCode 451. Sort Characters By Frequency

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.

分析：在cnt数组中保存每个字母出现的次数，然后按照出现次数的顺序对字符串进行排序～

class Solution {
public:
    string frequencySort(string s) {
        int cnt[256] = {0};
        for(int i = 0; i < s.length(); i++)
            cnt[s[i]]++;
        sort(s.begin(), s.end(), [&](char a, char b) {
            return cnt[a] > cnt[b] || (cnt[a] == cnt[b] && a < b);
        });
        return s;
    };
};

class Solution {

public:

string frequencySort(string s) {

int cnt[256] = {0};

for(int i = 0; i < s.length(); i++)

cnt[s[i]]++;

sort(s.begin(), s.end(), [&](char a, char b) {

return cnt[a] > cnt[b] || (cnt[a] == cnt[b] && a < b);

});

return s;

};

❤ 点击这里 -> 订阅《PAT | 蓝桥 | LeetCode学习路径 & 刷题经验》by 柳婼

❤ 点击这里 -> 订阅《从放弃C语言到使用C++刷算法的简明教程》by 柳婼

❤ 点击这里 -> 订阅PAT甲级乙级、蓝桥杯、GPLT天梯赛、LeetCode题解离线版