Heap_Sort金老师模板

#include <iostream>
using namespace std;

//根据需求调整大小
#define SIZE 1001
int heap[SIZE];

#define swap(x, y) {x = x + y; y = x - y; x = x - y;}

void fixDown(int heap[], int pos, int size){

    int x = pos;
    if(x > size) return;//exit

    // 选出最大的
    int l = 2 * x;
    int r = l + 1;
    int maxPos = x;
    if(l <= size && heap[maxPos] < heap[l]) maxPos = l;
    if(r <= size && heap[maxPos] < heap[r]) maxPos = r;

    if(maxPos != x){ //如果父节点不是最大的，进行互换，并在新的点上继续fixDown
        swap(heap[x], heap[maxPos]);
        fixDown(heap, maxPos, size);
    }
}

void fixUp(int heap[], int size, int pos){
    int x = pos;
    int p;
    while(x > 1){
        p = x/2;
        if(heap[x] > heap[p]){
            swap(heap[x], heap[p]);
            x = p;
        }else return;
    }
}

void buildHeap(int heap[], int size){
    for(int i = size/2; i >= 1; i--){
        fixDown(heap, i, size);
    }
}

//heapSort前要先build heap
void heapSort(int heap[], int size){
    int oriSize = size;
    for(int i = 0; i < oriSize - 1; i++){ //注意不要把oriSize和size混在一起
        //互换堆顶和最后一个元素，将堆顶元素放在数组最后面
        swap(heap[size], heap[1]);
        size--;
        fixDown(heap, 1, size);
    }
}

int main(){
    int size = 7;
    for(int i = 1; i <= size; i++) heap[i] = 8 - i;
    buildHeap(heap, size);
    heap[size + 1] = 8;
    size++;
    fixUp(heap, size, size);
    heapSort(heap, size);
}

POJ3481