今天偶然看到一个找出N个数中最大的前500个数，一个不错的解法是使用堆来进行选择，每一次读取一个数判断是否需要放到堆中，这样比较下来就可以找到最大或最小的前500个数了，自己晚上就参考别人的代码写了一个最小堆的结构，后期继续补充。

#include 
      
        #include 
       
         typedef int ElemType; struct heap{
        ElemType *num; int heapsize; int maxSize; }; struct heap HP; int init_heap(int size) {
    if(size <= 0){
                printf("not allow empty heap\n"); return -1;     }     HP.num = malloc(size*sizeof(ElemType)); if(HP.num == NULL){
                printf("malloc failed\n");             exit(1);     }     HP.heapsize = 0;     HP.maxSize = size; return 0; } void exit_heap() {
    if(HP.num != NULL){
            free(HP.num);         HP.num = NULL;         HP.heapsize = 0;         HP.maxSize = 0;     } } int isEmpty() {
    if(HP.heapsize == 0){
    return 1;     }else{
    return 0;     } } int insert_heap(ElemType arg) {
    int ct; if(HP.heapsize == HP.maxSize){
            ElemType* pe;         pe = realloc(HP.num,HP.heapsize*2*sizeof(ElemType)); if(pe == NULL){
                printf("realloc heap failed\n");             exit(1);         }         HP.num = pe;         HP.maxSize = HP.heapsize*2;     }     HP.num[HP.heapsize] = arg;     HP.heapsize++;     ct = HP.heapsize - 1; while(0 != ct){
    int j = (ct - 1) /2; if(arg > HP.num[j])  break;         HP.num[ct] = HP.num[j];         ct = j;     }     HP.num[ct] = arg; return 1; } ElemType delete_heap() {
          ElemType temp,x; int i,j; if(HP.heapsize == 0){
                printf("heap has been empty\n");             exit(1);        }        x = HP.num[0];        HP.heapsize--; if(HP.heapsize == 0){
    return x;         }         temp = HP.num[HP.heapsize];         i = 0;         j = 2*i + 1; while(j <= HP.heapsize-1){
    if((j< HP.heapsize-1) && (HP.num[j] > HP.num[j+1])){
                        j++;             } if(temp <= HP.num[j] ){
    break;             }             HP.num[i] = HP.num[j];             i = j;             j = 2*i + 1;         }         HP.num[i] = temp; return x; } int main() {
    int i;     ElemType it;     printf("input:"); for(i=0;i<10;i++){
            scanf("%d",&it);         insert_heap(it);     } for(i=0;i<10;i++){
            printf("%d ",delete_heap());     }     printf("\n"); return 0; }