problem with prime numbers

[amir20001]

code:

#include <iostream> using namespace std; int main() {     int max=999; // set the size of the array     bool prime [max];     int num[max];     for (int i=-1;i<max;i++)     {         num[i]=i+2;//seting the numbers in the arry     }     for (int j=-1;j<max;j++)     {         prime[j]=true;//seting the numbers in the arry     }     prime[0]=false; ///////////////////////////////////////////// //what this part is supose to do is go througe and see witch numbers are considered prime and removing //all multiples of that number but it dose not work can any one tell me why     for (int k=0;k<max;k++)     {         if (prime[k])/        cout <<num[k];             for (int i=0;i<max;i=i+num[k])             {                 //cout<<(num[i]%num[k]==0);                 prime[i]=false;             } //////////////////////////////////////////////////     }    /* for (int i=-1;i<max;i++) // for each element in the array     {         if (prime[i])             cout<<num[i]<<endl;     } */     return 0; }

This is probably something obvious but i dont understand whats wrong with it can some one explain it for me.
thx in advance

[DemonWasp]

The if (prime[k]) line is missing its block ( curly braces - { and } ) and therefore only affects the line after it, which is an output line. Based on the indenting, you want a block around the contained for(){} loop.

[Barbarrosa]

Based on my current understanding, this block of code alters the area one space before each array. I don't believe that's what you intended to do, so you should probably start those loops at or after zero.

c++:

int main() {     int max=999; // set the size of the array     bool prime [max];     int num[max];     for (int i=-1;i<max;i++)     {         num[i]=i+2;//seting the numbers in the arry     }     for (int j=-1;j<max;j++)     {         prime[j]=true;//seting the numbers in the arry     }     prime[0]=false;