05-树7 堆中的路径

Posted 2020-10-17

题目

输入样例:
5 3
46 23 26 24 10
5 4 3
输出样例:
24 23 10
46 23 10
26 10

基本思路

实现小顶堆时，可以把输入变为负数输入大顶堆。

代码

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
using namespace std;
class Heap  //大顶堆
{
public:
    int *elm;
    int size;
    Heap( int z) :size(z){ elm = new int[z]; }
    Heap(int* a,int z) :size(z)
    {
        elm = new int[z];
        for (int i = 1; i <= size; i++)
        {
            elm[i] = a[i];
        }
        for (int i = size / 2; i >= 1; i--) {
            downAdjust(i);
        }
    }
    void downAdjust(int dst);
    void upAdjust(int dst);
    void insert(int X,int i) {
        
        elm[i] = X;
        upAdjust(i);
    }
     
};




void swap(int &a, int &b)
{
    int temp;
    temp = a;
    a = b;
    b = temp;
}


int main()
{
    int N, M;
    cin >> N;
    cin >> M;
    
    Heap heap( N);
    for (int i = 1; i <= N; i++)
    {
        int temp;
        cin >> temp;
        heap.insert(-temp, i);
    }
    
    int *out = new int[M];
    for (int i = 0; i < M; i++)
    {
        int temp;
        cin >> temp;
        out[i] = temp;
    }
    for (int i = 0; i <M; i++)
    {
        int k= out[i];
        while (k > 1)
        {
            cout << -heap.elm[k]<<' ';
            k /= 2;
        }
        cout << -heap.elm[1] << endl;
    }
    return 0;
}

void Heap::downAdjust(int dst)
{
    int now = dst, lchild = 2 * dst,child=lchild;
    while (lchild <= size)
    {
        if (lchild + 1 <= size&&elm[lchild+1]>elm[lchild])
        {
            child = lchild + 1;
        }
        if (elm[child] > elm[now])         //孩子的权值比当前结点大
        {
            swap(elm[child], elm[now]);    //交换位置
            now = child;
            lchild = 2 * now;
            child = lchild;
        }
        else                 
            break;                        //停止调整
    }
}

void Heap::upAdjust(int dst)
{
    int now = dst, father = now / 2;
    while (father >= 1)
    {
        if (elm[now] > elm[father]) {
            swap(elm[now], elm[father]);
            now = father;
            father = now / 2;
        }
        else
            break;
    }
}

总结