哈夫曼树优先队列

哈夫曼树其实可以视为大顶堆（从大到小的二叉树），从叶到根，分别取优先队列中最小的俩个数进行和值，构成小型二叉树不断循环往上。

#include <bits/stdc++.h>
using namespace std;
string s;
int num[30];
int bfs()
{
    int a, b, sum = 0;
    priority_queue<int, vector<int>, greater<int>> q;//从小到大
    for (int i = 0; i < 27; i++)
    {
        if (num[i])
            q.push(num[i]);
    }
    if (q.size() == 1)
        sum = q.top();
    while (q.size() > 1)
    {
        a = q.top();
        q.pop();
        b = q.top();
        q.pop();
        sum += a + b;
        q.push(a + b);
    }
    return sum;
}
int main()
{
    while (cin >> s)
    {
        if (s == "END")
            break;
        memset(num, 0, sizeof num);
        int len = s.size();
        for (int i = 0; i < len; i++)
        {
            if (s[i] == '_')
                num[26]++;
            else
                num[s[i] - 'A']++;
        }
        int res = bfs();
        cout << len * 8 << ' ' << res << ' ' << len * 8 * 1.0 / res << '\n';
    }
    return 0;
}