title
题目与link类似
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.
solution
class Solution {
public:
string frequencySort(string s) {
unordered_map<char, int> map1;
for (char c : s) {
map1[c]++;
}
vector<vector<char>> v(s.length() + 1);
for (auto it : map1) {
v[it.second].push_back(it.first);
}
string res = "";
for (int i = v.size() - 1; i >= 0; i--) {
for (char c : v[i]) {
for(int j=0;j<i;j++)
res += c;
}
}
return res;
}
};