PAT A 1078. Hashing (25)

题目

The task of this problem is simple: insert a sequence of distinct positive integers into a hash table, and output the positions of the input numbers.  The hash function is defined to be "H(key) = key % TSize" where TSize is the maximum size of the hash table.  Quadratic probing (with positive increments only) is used to solve the collisions.

Note that the table size is better to be prime.  If the maximum size given by the user is not prime, you must re-define the table size to be the smallest prime number which is larger than the size given by the user.

Input Specification:

Each input file contains one test case.  For each case, the first line contains two positive numbers: MSize (<=10⁴) and N (<=MSize) which are the user-defined table size and the number of input numbers, respectively.  Then N distinct positive integers are given in the next line.  All the numbers in a line are separated by a space.

Output Specification:

For each test case, print the corresponding positions (index starts from 0) of the input numbers in one line.  All the numbers in a line are separated by a space, and there must be no extra space at the end of the line.  In case it is impossible to insert the number, print "-" instead.

Sample Input:

4 4
10 6 4 15

Sample Output:

0 1 4 -

 

将数据插入哈希表，使用平方探测处理碰撞；如果用户指定的哈希表大小不是质数，则寻找大于该值的最大质数。

 

代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

bool Is_prime(int n);	//检验质数

int main()
{
	int msize,n;
	cin>>msize>>n;
	while(!Is_prime(msize))	//获取符合要求的大小
		msize++;
	
	int i,j;
	int* flag=new int [msize];	//相应位置是否有数，0无，1有
	for(i=0;i<msize;i++)
		flag[i]=0;

	int temp,index;	//输入的数，序号
	scanf("%d",&temp);	//处理第一个
	index=temp%msize;
	flag[index]=1;
	printf("%d",index);
	for(i=1;i<n;i++)	//处理后面的
	{
		scanf("%d",&temp);
		for(j=0;j<msize;j++)	//二次探测
		{
			index=(temp+j*j)%msize;
			if(flag[index]==0)
			{
				flag[index]=1;
				printf(" %d",index);
				break;
			}
		}
		if(j>=msize)
			printf(" -");
	}

	delete [] flag;

	return 0;
}

bool Is_prime(int n)	//判断质数
{
	if(n==0||n==1)
		return false;
	if(n==2)
		return true;
	int limit=(int)sqrt((double)n);
	for(int i=2;i<=limit;i++)
	{
		if(n%i==0)
			return false;
	}
	return true;
}