增加桥和割点的说明和编程实现，以及非遍历树边，前向树，后向树的简单介绍（add bridge and cut point,etc）

Author: AlexJakin

Bridges/__init__.py

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+"""
+@author: Alex
+@contact: 1272296763@qq.com or jakinmili@gmail.com
+@file: __init__.py.py
+@time: 2019/11/13 20:54
+"""
+

Bridges/findBridges.py

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+"""
+@author: Alex
+@contact: 1272296763@qq.com or jakinmili@gmail.com
+@file: findBridges.py
+@time: 2019/10/20 19:12
+"""
+class findBridges:
+
+    def __init__(self, filename):
+        self.V = 0  # 顶点数
+        self.E = 0  # 边数
+        self.adj = None
+
+
+
+        with open(filename) as f:
+            line_num = 0  # 第一行是顶点数和边数
+            for line in f:
+                if line_num == 0:
+                    v, e = line.strip().split()
+                    self.V = int(v)
+                    self.E = int(e)
+                    self.adj = [[] for i in range(self.V)] # 创建二维数组即邻接表
+                else:
+                    # 读取边 写入邻接表
+                    v1, v2 = line.strip().split()
+                    # 转化为整数
+                    v1 = int(v1)
+                    v2 = int(v2)
+                    self.adj[v1].append(v2)
+                    self.adj[v2].append(v1)
+                line_num += 1
+
+        self.__visited = [False for i in range(self.V)]
+        self.__ord = [0 for i in range(self.V)]
+        self.__low = [0 for i in range(self.V)]
+        self.__cnt = 0
+        self.res = []
+
+
+        # 各个联通分量寻找桥
+        for v in range(self.V):
+            if self.__visited[v] == False:
+                self.graphDFS(v, v)
+
+    def get_graph_information(self):
+        """
+        打印图的邻接表
+        :return:
+        """
+        print("V={}, E={}".format(self.V, self.E))
+        for i, v in enumerate(self.adj):
+            print("{} : {}".format(i, v))
+
+    def validateVertex(self, v):
+        """
+        验证顶点取值
+        :param v:
+        :return:
+        """
+        if v<0 or v>=self.V:
+            raise ValueError("v值超出范围")
+
+    def hasEdge(self, v, w):
+        """
+        判断两个顶点是否存在
+        :param v: 第一个顶点
+        :param w: 第二个顶点
+        :return: true or false
+        """
+        self.validateVertex(v)
+        self.validateVertex(w)
+        return w in self.adj[v]
+
+    def degree(self, v):
+        """
+        求某个顶点的度
+        :param v:
+        :return:
+        """
+        self.validateVertex(v)
+        return len(self.adj[v])
+
+
+    def graphDFS(self, v, parent):
+
+        # 标记v顶点已经遍历过了
+        self.__visited[v] = True
+        self.__ord[v] = self.__cnt
+        self.__low[v] = self.__ord[v]
+        self.__cnt+=1
+        # 添加
+        for w in self.adj[v]:
+            if self.__visited[w] == False:
+                self.graphDFS(w, v)
+                self.__low[v] = min(self.__low[v], self.__low[w])
+                if self.__low[w] > self.__ord[v]:
+                    # v-w是桥
+                    self.res.append("{}-{}".format(v,w))
+
+            elif w != parent:
+                self.__low[v] = min(self.__low[v], self.__low[w])
+
+    def  findBridges(self):
+        print("该联通分量有存在桥的有：", self.res)
+
+if __name__ == '__main__':
+    fb = findBridges("../g_bridges2.txt")
+    fb.get_graph_information()
+    fb.findBridges()
+
+    fb1 = findBridges("../tree.txt")
+    fb1.get_graph_information()
+    fb1.findBridges()

Bridges/findCutPoint.py

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+"""
+@author: Alex
+@contact: 1272296763@qq.com or jakinmili@gmail.com
+@file: findCutPoint.py
+@time: 2019/10/20 19:12
+"""
+class findCutPoint:
+
+    def __init__(self, filename):
+        self.V = 0  # 顶点数
+        self.E = 0  # 边数
+        self.adj = None
+
+
+
+        with open(filename) as f:
+            line_num = 0  # 第一行是顶点数和边数
+            for line in f:
+                if line_num == 0:
+                    v, e = line.strip().split()
+                    self.V = int(v)
+                    self.E = int(e)
+                    self.adj = [[] for i in range(self.V)] # 创建二维数组即邻接表
+                else:
+                    # 读取边 写入邻接表
+                    v1, v2 = line.strip().split()
+                    # 转化为整数
+                    v1 = int(v1)
+                    v2 = int(v2)
+                    self.adj[v1].append(v2)
+                    self.adj[v2].append(v1)
+                line_num += 1
+
+        self.__visited = [False for i in range(self.V)]
+        self.__ord = [0 for i in range(self.V)]
+        self.__low = [0 for i in range(self.V)]
+        self.__cnt = 0
+        self.res = set()
+
+
+        # 各个联通分量寻找桥
+        for v in range(self.V):
+            if self.__visited[v] == False:
+                self.graphDFS(v, v)
+
+    def get_graph_information(self):
+        """
+        打印图的邻接表
+        :return:
+        """
+        print("V={}, E={}".format(self.V, self.E))
+        for i, v in enumerate(self.adj):
+            print("{} : {}".format(i, v))
+
+    def validateVertex(self, v):
+        """
+        验证顶点取值
+        :param v:
+        :return:
+        """
+        if v<0 or v>=self.V:
+            raise ValueError("v值超出范围")
+
+    def hasEdge(self, v, w):
+        """
+        判断两个顶点是否存在
+        :param v: 第一个顶点
+        :param w: 第二个顶点
+        :return: true or false
+        """
+        self.validateVertex(v)
+        self.validateVertex(w)
+        return w in self.adj[v]
+
+    def degree(self, v):
+        """
+        求某个顶点的度
+        :param v:
+        :return:
+        """
+        self.validateVertex(v)
+        return len(self.adj[v])
+
+
+    def graphDFS(self, v, parent):
+
+        # 标记v顶点已经遍历过了
+        self.__visited[v] = True
+        self.__ord[v] = self.__cnt
+        self.__low[v] = self.__ord[v]
+        self.__cnt+=1
+
+        child = 0
+        # 添加
+        for w in self.adj[v]:
+            if self.__visited[w] == False:
+                self.graphDFS(w, v)
+                self.__low[v] = min(self.__low[v], self.__low[w])
+
+                # 割点检测
+                if v != parent and self.__low[w] >= self.__ord[v]:
+                    self.res.add(v)
+
+                child += 1
+
+                if v == parent and child>1: # 如果是根节点
+                    self.res.add(v)
+
+            elif w != parent:
+                self.__low[v] = min(self.__low[v], self.__low[w])
+
+    def findCutPoint(self):
+        print("该联通分量有存在割点的有：", self.res)
+
+if __name__ == '__main__':
+    fb = findCutPoint("../g_bridges2.txt")
+    fb.get_graph_information()
+    fb.findCutPoint()
+
+    fb1 = findCutPoint("../tree.txt")
+    fb1.get_graph_information()
+    fb1.findCutPoint()

Floodfill/Solution.py

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+"""
+@author: Alex
+@contact: 1272296763@qq.com or jakinmili@gmail.com
+@file: Solution.py
+@time: 2019/10/27 13:38
+"""
+
+class Solution(object):
+
+    def __init__(self):
+        self.__R = 0 # row
+        self.__C = 0 # colum
+        self.dirs = [
+            [-1, 0], [0, 1], [1, 0], [0, -1]
+        ]
+        self.visited = []
+        self.grid = []
+        self.G = []
+
+    def maxAreaOfIsland(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: int
+        """
+        if grid == None: return 0
+        self.__R = len(grid)
+        if self.__R == 0: return 0
+        self.__C = len(grid[0])
+        if self.__C == 0: return 0
+        self.grid = grid
+
+        self.G = self.constructGraph()
+        # 对每一个陆地进行遍历
+        res = 0
+        self.visited = [False for i in range(len(self.G))]
+        for v in range(len(self.G)):
+            x = int(v / self.__C)
+            y = v % self.__C
+            if self.grid[x][y] == 1 and self.visited[v] == False:
+                res = max(res, self.dfs(v))
+        return res
+
+    def dfs(self, v):
+        self.visited[v] = True
+        res = 1
+        for w in self.G[v]:
+            if self.visited[w] == False:
+                res += self.dfs(w)
+        return res
+
+
+    def constructGraph(self):
+        g = [[] for i in range(self.__R * self.__C)]
+
+        # 二维转一维
+        for v in range(len(g)):
+            x = int(v / self.__C)
+            y = v % self.__C
+            # 一维表中某个位置计算出的(x, y) 代表 二维表中的坐标
+            if self.grid[x][y] == 1:
+                # 对(x, y)四个方向都进行观察，看看是否有陆地
+                # 如果有，在邻接表中相应位置 增加一条边
+                for d in self.dirs:
+                    next_x = x + d[0]
+                    next_y = y + d[1]
+                    if self.inArea(next_x, next_y) and self.grid[next_x][next_y] :
+                        next = next_x * self.__C + next_y
+                        g[v].append(next)
+                        g[next].append(v)
+        return g
+
+    def inArea(self, x, y):
+        return x >= 0 and x < self.__R and y >= 0 and y < self.__C
+
+
+
+if __name__ == '__main__':
+    obj = Solution()
+    print(obj.maxAreaOfIsland([[0,0,1,0,0,0,0,1,0,0,0,0,0],
+ [0,0,0,0,0,0,0,1,1,1,0,0,0],
+ [0,1,1,0,1,0,0,0,0,0,0,0,0],
+ [0,1,0,0,1,1,0,0,1,0,1,0,0],
+ [0,1,0,0,1,1,0,0,1,1,1,0,0],
+ [0,0,0,0,0,0,0,0,0,0,1,0,0],
+ [0,0,0,0,0,0,0,1,1,1,0,0,0],
+ [0,0,0,0,0,0,0,1,1,0,0,0,0]]))