HDU 2648 Shopping

Shopping

Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 2126 Accepted Submission(s): 712



Problem Description

Every girl likes shopping,so does dandelion.Now she finds the shop is increasing the price every day because the Spring Festival is coming .She is fond of a shop which is called "memory". Now she wants to know the rank of this shop's price after the change
of everyday.

Input

One line contians a number n ( n<=10000),stands for the number of shops.

Then n lines ,each line contains a string (the length is short than 31 and only contains lowercase letters and capital letters.)stands for the name of the shop.

Then a line contians a number m (1<=m<=50),stands for the days .

Then m parts , every parts contians n lines , each line contians a number s and a string p ,stands for this day ,the shop p 's price has increased s.

Output

Contains m lines ,In the ith line print a number of the shop "memory" 's rank after the ith day. We define the rank as :If there are t shops' price is higher than the "memory" , than its rank is t+1.

Sample Input

3
memory
kfc
wind
2
49 memory
49 kfc
48 wind
80 kfc
85 wind
83 memory

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=2648

~~~自己的第一道字符串hash，接触到了BKDRHash函数，网上百度了许多似乎没有对它进行太多的解释，因此我也就拿来用用，里面的seed=31没怎么理解，似乎是为了让hash值更分散从而减少冲突，key是记录hash值，最后的key&0x7fffffff好像只是为了让key得到一个整型的值，但是后面还是要对它进行取模，所以为什么中间不能对它取模呢，还是有些不理解的地方，希望以后会有机会解释这些。现在就先这样用着吧。

题目大意:有很多商店，有样物品在每个商店的价钱都不一样，而且每天这个物品的价钱都会增加，要求一个叫“memory”商店里的这个物品价格在所有商店里排在第几位（价格越低排在越前）。

题目思路:因为商店数n是10的4次方，暴力比较的话会超时，所以用字符串hash先记录每个商店的位置，用vector定义动态二维数组记录，这样遇到冲突的hash值也可以处理。

然后就是输入和更新了，这题目会用到许多变量，所以初始化和使用时还是要仔细点的。具体实现可以直接看代码。

AC代码:

#include<iostream>
#include<cstdio>
#include<vector>
#include<cstring>
using namespace std;
#define N 10005
struct node{
char name[35];
int price;
node(){
price=0;
}
};
int p
;
vector<node>List
;
unsigned int BKDRHash(char *str){
unsigned int seed = 31,key = 0;
while(*str){
key=key*seed+*str++;
}
return key&0x7fffffff;
}
int main(){
int n,m,k,add,memory_price,tot,len;
char s[35];
node t;
while(scanf("%d",&n)!=EOF){
for(int i=0;i<N;i++){
List[i].clear();
}
for(int i=0;i<n;i++){
scanf("%s",t.name);
k=BKDRHash(t.name)%N;
List[k].push_back(t);
}
scanf("%d",&m);
while(m--){
tot=len=0;
for(int i=0;i<n;i++){
scanf("%d%s",&add,s);
k=BKDRHash(s)%N;
for(int j=0;j<List[k].size();j++){
if(strcmp(List[k][j].name,s)==0){

List[k][j].price+=add;
if(strcmp(s,"memory")==0)
memory_price=List[k][j].price;
else
p[len++]=List[k][j].price;
break;
}
}
}
for(int i=0;i<len;i++){
if(memory_price<p[i]) tot++;
}
printf("%d\n",tot+1);
}
}
return 0;
}