leetcode1042 Flower Planting With No Adjacent

 """
 You have N gardens, labelled 1 to N.  In each garden, you want to plant one of 4 types of flowers.
 paths[i] = [x, y] describes the existence of a bidirectional path from garden x to garden y.
 Also, there is no garden that has more than 3 paths coming into or leaving it.
 Your task is to choose a flower type for each garden such that, for any two gardens connected by a path, they have different types of flowers.
 Return any such a choice as an array answer, where answer[i] is the type of flower planted in the (i+1)-th garden.  The flower types are denoted 1, 2, 3, or 4.  It is guaranteed an answer exists.
 Example 1:
 Input: N = 3, paths = [[1,2],[2,3],[3,1]]
 Output: [1,2,3]
 Example 2:
 Input: N = 4, paths = [[1,2],[3,4]]
 Output: [1,2,1,2]
 Example 3:
 Input: N = 4, paths = [[1,2],[2,3],[3,4],[4,1],[1,3],[2,4]]
 Output: [1,2,3,4]
 """
 """
 此题用贪心算法
 没掌握
 """
 class Solution(object):
     def gardenNoAdj(self, N, paths):
         res = [0] * N
         m = [[] for i in range(N + 1)]  # 用来存第i个结点到其他结点的路径，i为1到N
         for x, y in paths:
             m[x].append(y)
             m[y].append(x)
         for i in range(1, N + 1):  # 对N个路径进行遍历
             used = set()  # 用来存这个结点出现的所有路径使用过的颜色
             for j in m[i]:
                 used.add(res[j - 1])  # 把目的地的颜色放入used里
             for j in range(1, 5):  # 1，2，3，4代表四种颜色
                 if j not in used:
                     res[i - 1] = j  # 将该结点存入新的颜色
                     break
         return res