哈夫曼建树

模板

建哈夫曼树方法

//哈夫曼树的构造
#include <iostream>
#include <queue>
using namespace std;

//树的节点
struct node{
    int num;//该点权值
    node* l;
    node* r;
};

//哈夫曼树根节点
node* root;

struct cmp{
    bool operator () (node* a, node* b){
        return a-> num > b-> num;
    }
};

priority_queue<node*, vector<node*>, cmp> q;

//建树思想：最开始每个节点都是一棵树，
//然后选最小权值的根节点2个，并移除这2个节点，
//将他们并成新树，加入到优先队列中
void create(){
    //直到只剩一棵树时停止
    while(q.size() > 1){
        node* node1 = q.top();
        q.pop();
        node* node2 = q.top();
        q.pop();

        node* sum = new node();
        sum->l = node1;
        sum->r = node2;
        sum->num = node1->num+node2->num;

        root = sum;
        q.push(sum);
    }
}

//遍历哈夫曼树，求WPL
long long dfs(node* node1){
    if(node1->l == NULL){
        return 0;
    }
    else{
        return dfs(node1->l)+dfs(node1->r)+node1->num;
    }
}

int main()
{
    int n, num;
    while(cin >> n){
        while(n--){
            cin >> num;
            node* data = new node();
            data->l=data->r = NULL;
            data->num = num;
            q.push(data);
        }
        create();
        if(n == 1) cout << 0 << endl;
        else{
            long long result = dfs(root);
            cout << result << endl;
        }
        while(q.size()) q.pop();
    }
    return 0;
}
//POJ3253 G++

不建树的哈夫曼，思想和哈夫曼建树思想类似

#include <iostream>
#include <queue>
using namespace std;
int main()
{
    int n, num;
    priority_queue<int, vector<int>, greater<int> > q;
    while(cin >> n){
        while(n--){
            cin >>num;
            q.push(num);
        }
        long long sum = 0;
        while(q.size() > 1){
            int num1 = q.top();
            q.pop();
            int num2 = q.top();
            q.pop();
            int he = num1 + num2;
            sum+=he;
            q.push(he);
        }
        cout << sum << endl;
        while(q.size())q.pop();
    }
    return 0;
}
//POJ3252