优先队列的实现

        STL中有priority_queue可以实现优先队列。

        下面的代码是小堆哦，是从小到大的顺序。

#include <stdio.h>#define MAX_N 2001int heap[MAX_N];int size;void push(int x) {int i = size++;int p;while (i > 0) {p = (i - 1) / 2;if (heap[p] < x) {break;}heap[i] = heap[p];i = p;}heap[i] = x;}int pop() {int res = heap[0];int x = heap[--size];int i = 0;int a, b;while (i*2 + 1 < size) {a = i*2 + 1;b = i*2 + 2;if (b < size && heap[b] < heap[a]) {a = b;}if (heap[a] >= x) {break ;}heap[i] = heap[a];i = a;}heap[i] = x;return res;}int main() {int a[] = {8, 4, 3, 5, 6, 7, 9};int i;for (i = 0; i < 7; i++) {push(a[i]);}for (i = 0; i < 7; i++) {printf("%d  ", pop());}printf("\n");return 0;}