题解 | 【模板】堆

#include <stdio.h>
#include <stdlib.h>
void swap(int* a, int m, int n) {
    int temp;
    temp = a[m];
    a[m] = a[n];
    a[n] = temp;
}
void push(int* a, int x, int* length) {
    if (*length == 0) {
        a[0] = x;
        (*length)++;
    } else {
        int flag = *length;
        a[flag] = x;
        (*length)++;
        while (flag > 0 && a[(flag - 1) / 2] < a[flag]) {
            swap(a, flag, (flag - 1) / 2);
            flag = (flag - 1) / 2;
        }
    }
}
void top(int* a, int* length) {
    if (*length == 0) {
        printf("empty\n");
    } else {
        printf("%d\n", a[0]);
    }
}
void pop(int* a, int* length) {
    if (*length == 0) {
        printf("empty\n");
    } else {
        printf("%d\n", a[0]);
        a[0] = a[(*length) - 1];
        (*length)--;
        int flag = 0;
        while (1) {
            int left = 2 * flag + 1;
            int right = 2 * flag + 2;
            int max = flag;
            if (left < *length && a[left] > a[max]) {
                max = left;
            }
            if (right < *length && a[right] > a[max]) {
                max = right;
            }
            if (max != flag) {
                swap(a, flag, max);
                flag = max;
            } else {
                break;
            }
        }
    }
}
int main() {
    int n;
    int x;
    int a[100000];
    int length = 0;
    char s[5];
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%s", s);
        if (s[0] == 'p' && s[1] == 'u') {
            scanf("%d", &x);
            push(a, x, &length);
        } else if (s[0] == 't') {
            top(a, &length);
        } else if (s[0] == 'p' && s[1] == 'o') {
            pop(a, &length);
        }
    }
    return 0;
}