Solve eight queen (both recursively and non-recursively)

#include <iostream>
#include <cmath>
#include <cstdlib>
#include <cstdio>
using namespace std;
#define N 8

//Check whether s[k] = pos is ok
bool is_ok(int s[], int k, int pos)
{
    for(int i=0; i<k; i++){
        if(pos == s[i] ) return false;
        if(abs(s[i]-pos) == abs(k-i) )return false;
    }
    return true;
}


void output(int pos[])
{
    for(int i=0;i<N;i++)
        cout<<pos[i]<<",";
    cout<<endl;
}
void put(int i, int pos[])
{
    if(i==N){
        output(pos);
        return ;
    }
    for(int j=0;j<N;j++)
        if(is_ok(pos, i, j)){
            pos[i]=j;
            put(i+1, pos);
        }
    
}

void put2()
{
    int s[N]={-1};
    int i=0;s[0]=0;
    i++;
    while(i>=0)
    {
        int j;
        if(i==N){ 
            output(s); i--;
        }
        for(j= max(0, s[i]+1); j<N ;j++)
            if( is_ok(s, i, j)) {
                s[i] = j;i++; break;
            }
        if(j==N){
            s[i]=-1;i--;
        }
    }
}
int main()
{
    int pos[N]={0};
    put(0,pos);
    put2();
    return 0;
}