50167. E-commerce

#include <stdio.h>
#include "payment.h"
#define MAXN 20000

int get_size(int arr[]){
    int n = 1;
    while(arr[n] != 0) n++;
    return n;
}

int find_id(int id, int id_list[], int n){
    for(int i = 0; i < n; i++){
        if(id_list[i] == id) return i;
    }
    return -1;
}

int on_sale(int id, int on_sale_id[], int sale_len){
    for(int i = 0; i < sale_len; i++){
        if(id == on_sale_id[i]) return 1;
    }
    return 0;
}

double payment(int id_list[], double price[], int order_item_id[], int order_qty[], int on_sale_id[]){
    int n = get_size(id_list);
    int m = get_size(order_item_id);
    int sale_len = get_size(on_sale_id);

    double ans = 0;
    for(int i = 0; i < m; i++){
        int now_id = order_item_id[i], now_qty = order_qty[i];
        int idx = find_id(now_id, id_list, n);
        double now_price = price[idx];
        if(on_sale(now_id, on_sale_id, sale_len)) ans += now_price * now_qty * (double)0.8;
        else ans += now_price * now_qty;
    }

    if(ans < (double)490.00) ans += (double)80;
    return ans;
}