USACO Section 1.5 Checker Challenge

/*
ID: lucien23
PROG: checker
LANG: C++
*/

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int N;
int symPos;
int sum=0;
int count=0;
bool isCountComplete=false;
bool isPrintComplete=false;
int *position;

void generate(int row);

int main()
{
freopen("checker.in","r",stdin);
freopen("checker.out","w",stdout);

scanf("%d",&N);
symPos=N/2+N%2+1;
position=(int*)malloc(N*sizeof(int));
generate(0);
printf("%d\n",sum);
free(position);
return 0;
}

void generate(int row)
{
int *pPos=(int*)malloc(N*sizeof(int));
for(int i=0;i<N;i++)
{
pPos[i]=0;
}
for (int i=0;i<row;i++)
{
pPos[position[i]]=1;
}

for(int i=0;i<N;i++)
{//第row行的棋子放在第i列
if(row==0)
{
if(N%2==0 && i==symPos-1)
{//偶数列
sum*=2;
isCountComplete=true;
}else if(N%2==1 && i==symPos-2){
sum*=2;
}else if (N%2==1 && i==symPos-1){
isCountComplete=true;
}
}

if(isCountComplete && isPrintComplete)
return;

if(pPos[i])
continue;
int k;
for (k=0;k<row;k++)
{
if(abs(row-k)==abs(i-position[k]))
break;
}
if(k<row)
{//第row行的棋子不能放在第i列
continue;
}

position[row]=i;
if(row==N-1)
{
count++;
if(!isCountComplete)
sum++;
if(count<=3)
{
for (int j=0;j<N-1;j++)
{
printf("%d ",position[j]+1);
}
printf("%d\n",position[N-1]+1);
if(count==3)
isPrintComplete=true;
}
}else{
generate(row+1);
}
}
free(pPos);
}