Leetcode767 题目链接

解题思路

贪心：每次从堆中取出两个字母，并将对应的出现次数减一。

class Solution {
public:
    string reorganizeString(string S) {
        //2020.11.30
        unordered_map<char, int> hash;
        priority_queue<pair<int, char>> pq;
        for(auto c: S) hash[c]++;
        int count_max = 0;
        for(auto h: hash){
            count_max = max(count_max, h.second);
            pq.push({h.second, h.first});
        } 
        int n = S.size();
        // 奇数不应该超过(n+1)/2 偶数不应该超过n/2
        if(count_max > (n+1)/2) return "";
        // 使用优先队列 每次从堆中取两个数 保证不相邻
        string ans;
        while(pq.size() > 1){
            auto a = pq.top(); pq.pop();
            auto b = pq.top(); pq.pop();
            ans += a.second;
            ans += b.second;
            if(a.first > 1) pq.push({a.first-1, a.second});
            if(b.first > 1) pq.push({b.first-1, b.second});
        }
        if(pq.size()) ans += pq.top().second;
        return ans;
    }
};