Question:
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
C Code:
void main()
{
int prim[200000];
int no = 3;
int i =
7;
int j;
int mid = (int)sqrt(600851475143);
prim[1] =
2;
prim[2] = 3;
prim[3] = 5;
while(prim[no] <=
mid)
{
for(;;i++)
{
int flag = 1;
j =
1;
for(j = 1;j <= no;j++)
{
if(0 ==
i%prim[j])
{
flag =
0;
break;
}
}
if(flag)
{
no++;
prim[no]
= i;
i++;
break;
}
}
}
for(i =
no;i > 0;i--)
{
if(0 ==
600851475143%prim[i])
{
printf("%d\n",prim[i]);
}
}
}
Answer:
6857
ProjectEuler_P3,布布扣,bubuko.com
原文：http://www.cnblogs.com/zhoueh1991/p/3683356.html