堆

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堆是一种数组对象，维基百科。

堆实现代码：

#include<iostream>#include<vector>#include<algorithm>using namespace std;int heap_size;inline int LEFT(int i){return 2 * i + 1;}inline int RIGHT(int i){return 2 * (i + 1);}void display(int a[], int n){for (int i = 0; i < n; i++)cout << a[i] << " ";cout << endl;}void swap(int& n, int& m){int temp;temp = n;n = m;m = temp;}void max_heapify(int a[], int i){int l = LEFT(i);int r = RIGHT(i);int largest;if ((l < heap_size) && a[l] > a[i])largest = l;elselargest = i;if ((r < heap_size) && a[r] > a[largest])largest = r;/*if (largest != i){swap(a[largest], a[i]);max_heapify(a, largest);}*/while (largest!=i){swap(a[largest], a[i]);i = largest;l = LEFT(i);r = RIGHT(i);if (l<heap_size&&a[l]>a[i]){largest = l;}else{largest = i;}if (r<heap_size&&a[r]>a[i]){largest = r;}}}

int main(){<span style="white-space:pre"></span>int a[100];<span style="white-space:pre"></span>int n;<span style="white-space:pre"></span>while (cin >> n)<span style="white-space:pre"></span>{<span style="white-space:pre"></span>for (int i = 0; i < n; i++)<span style="white-space:pre"></span>cin >> a[i];<span style="white-space:pre"></span>heap_sort(a, n);<span style="white-space:pre"></span>display(a, n);<span style="white-space:pre"></span>}<span style="white-space:pre"></span>return 0;}

（2）在C++的STL中，有对堆的操作：点击打开链接。

代码如下：

int main(){int a[] = { 1,4,5,6,7,8,3,2 };vector<int> ivec(a, a + 5);for (vector<int>::iterator iter = ivec.begin();iter != ivec.end();iter++){cout <<*iter<<" " ;}cout << endl;make_heap(ivec.begin(), ivec.end());cout << "heap is :" << endl;for (vector<int>::iterator iter = ivec.begin();iter != ivec.end();iter++){cout << *iter << " ";}cout << endl;pop_heap(ivec.begin(), ivec.end());ivec.pop_back();cout << "after pop_back:" << endl;for (vector<int>::iterator iter = ivec.begin();iter != ivec.end();iter++){cout << *iter << " ";//cout << endl;}cout << endl;ivec.push_back(99);push_heap(ivec.begin(), ivec.end());cout << "after push_back:" << endl;for (vector<int>::iterator iter = ivec.begin();iter != ivec.end();iter++){cout << *iter << " ";//cout << endl;}cout << endl;sort_heap(ivec.begin(), ivec.end());cout << "after sorting:" << endl;for (vector<int>::iterator iter = ivec.begin();iter != ivec.end();iter++){cout << *iter << " ";//cout << endl;}cout << endl;return 0;}

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