HD-ACM算法专攻系列（18）——Largest prime factor

#include"iostream"
#include"memory.h"
#define MAX 1000000
using namespace std;

int index[MAX];

int main()
{
	
	memset(index, -1, sizeof(index));
	index[1] = 0;
	int sum = 0;
	for(int i = 2; i < MAX; i++)
	{
		if(index[i] == -1)
		{
			sum++;
			for(int j = i; j < MAX; j+= i)
			index[j]=sum;
		}
	}

	int n;
	while(scanf("%d", &n) != EOF)
		printf("%d\n", index[n]);
    return 0;
}