k路归并 算法导论8-4(e)

使用STL中priority_queue（由最大最小堆实现的）来实现。注意传递参数的时候需要传递三个。

模板声明：priority_queue<Type, Container, Functional>

这里的实现要求输入完全正确，所以代码移植性非常差。

#include <iostream>
#include <algorithm>
#include <queue>
using namespace std;

typedef struct {
    int key;
    int next;
}Likelist;

bool CompareLikelist(Likelist &i1,Likelist &i2){
    return i1.key > i2.key;
}

void K_Merge(int *a,int *b, int n, int k){
    priority_queue<Likelist,vector<Likelist>,decltype(CompareLikelist) *> pq(CompareLikelist);
    for (int i = 0; i < k; i++){
        if (i > n - 1)
            pq.push({ INT_MAX, 0 });
        else pq.push({ a[i], i + k });
    }
    for (int i = 0; i < n; ++i){
        Likelist temp = pq.top();
        b[i] = temp.key;
        pq.pop();
        if (temp.next>n - 1)
            pq.push({ INT_MAX, 0 });
        else pq.push({ a[temp.next], temp.next + k });
    }
}

int main(){
    int a[10] = { 33,1, 8, 45, 2, 9, 67, 10,9, 666 };
    int b[10];
    K_Merge(a, b, 10, 3);
    for (auto r : b)
        cout << r << " ";
}