Foundation of algorithms, p265

def n_queens(i, col):
    n = len(col) -1
    
    if (promising(i, col)):
        if( i == n):
            print(col[1:n+1])
        else:
            for j in range(1, n+1):
                col [i+1] = j
                n_queens(i+1, col) 
                
                
def promising(i, col):
    k = 1
    flag = True
    while(k < i and flag):
        if (col[i] == col[k] or abs(col[i]-col[k]) == (i-k)):
            flag = False
        k += 1
    return flag

n=4
col = [0]*(n+1)
n_queens(0, col)

[2, 4, 1, 3] [3, 1, 4, 2]