[python] N-Queen

https://school.programmers.co.kr/learn/courses/30/lessons/12952

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def n_queen(graph,x,n):
    result = 0
    if x == n:
        return 1
    for i in range(n):
        graph[x] = i
        if promising(graph,x):
            result += n_queen(graph, x+1, n)
    return result
        
def promising(graph,x):
    for i in range(x):
        if graph[x] == graph[i] or abs(graph[x] - graph[i]) == abs(x-i):
            return False
    return True
 
def solution(n):
    graph = [0] * n
    return n_queen(graph, 0, n)