符号三角形

#include <stdio.h>  
#define n 7
int sum;
int count;
int array[n+1][n+1];  
int half;
void traceback(int t)  
{ 
    if(t > n)
		sum++;  
  	
	if( (count > half) || ( t * (t-1) / 2 - count > half))  
        return;
    else {  
    	for (int i = 0; i < 2; i++) {  
            array[1][t] = i;  
            
			count = count + i;  
			for (int j = 2; j <= t; j++) {  
                array[j][t-j+1] = array[j-1][t-j+1] ^ array[j-1][t-j+2]; // 1^0 = 1           1^1 = 0 
                count += array[j][t-j+1];  
            }  

            traceback(t+1);  
            
			for (int j = 2; j <= t; j++)  
                count += array[j][t-j+1];  
            count-=i;  
        }  
    }  
}  
  
int main() {  
    
	half=(n+1)*n/2;  
	if(half%2==1) { 
		printf("%d", 0);
		return 0;
	}  

    traceback(1);  
    printf("%d\n",sum);  
    return 0;  
}