358. Rearrange String k Distance Apart

Given a non-empty string s and an integer k, rearrange the string such that the same characters are at least distance k from each other.

All input strings are given in lowercase letters. If it is not possible to rearrange the string, return an empty string "".

Example 1:

s = "aabbcc", k = 3

Result: "abcabc"

The same letters are at least distance 3 from each other.

 

Example 2:

s = "aaabc", k = 3 

Answer: ""

It is not possible to rearrange the string.

本题和task shceduler 一样的思路。

class Solution {
    struct mycompare{
        bool operator()(pair<int, char>& p1, pair<int, char>& p2){
            if(p1.first == p2.first) return p1.second > p2.second;//字母升序
            return p1.first < p2.first;//数字大小降序排列
        }
    };
public:
    string rearrangeString(string str, int k) {
        if(k == 0) return str;
        unordered_map<char, int> dict;
        for(char ch : str) dict[ch]++;
        int left = (int)str.size();
        priority_queue<pair<int, char>, vector<pair<int, char>>, mycompare > pq;
        for(auto it = dict.begin(); it != dict.end(); it++){
            pq.push(make_pair(it->second, it->first));
        }
        string res;
        
        while(!pq.empty()){
            vector<pair<int, char>> cache;
            int count = min(k, left);
            for(int i = 0; i < count; i++){
                if(pq.empty()) return "";
                auto tmp = pq.top();
                pq.pop();
                res.push_back(tmp.second);
                if(--tmp.first > 0) cache.push_back(tmp);
                left--;
            }
            for(auto p : cache){
                pq.push(p);
            }
        }
        return res;
    }
};

 

 

Example 3:

s = "aaadbbcc", k = 2

Answer: "abacabcd"

Another possible answer is: "abcabcda"

The same letters are at least distance 2 from each other.