递归和回溯_leetcode417

#coding=utf-8

# floodfill经典题

# step 1) 从太平洋的边界出发，找到所有能到达太平样的点 TP
# step 2) 从大西洋的边界出发，找到所有能到达大西洋的点 DX
# step 3) 求交集 TP DX

class Solution(object):
    def pacificAtlantic(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[List[int]]
        """

        self.res = []

        if not matrix:
            return self.res


        self.m = len(matrix)
        self.n = len(matrix[0])

        self.derecToPacific = [[0,1],[1,0]]
        self.derecToAtlantic = [[0,-1],[-1,0]]

        self.visitPacific = [[False for i in range(self.n)] for i in range(self.m)]
        self.visitAtlantic = [[False for i in range(self.n)] for i in range(self.m)]

        self.PacificStart = []
        self.AtlanticStart = []

        for y in range(self.n):
            self.PacificStart.append([0,y])
            self.AtlanticStart.append([self.m-1,y])
        for x in range(self.m):
            self.PacificStart.append([x,0])
            self.AtlanticStart.append([x,self.n-1])

        # for x in range(self.m):
        #     self.AtlanticStart.append([x, self.n - 1])
        # for y in range(self.n):
        #     self.AtlanticStart.append([self.m-1, y])

        # test
        self.toPacific(matrix)
        print  self.visitPacific

        self.toAtlantic(matrix)
        print  self.visitAtlantic

        # self.toPacific(matrix)
        # self.toAtlantic(matrix)
        #
        # for x in range(self.m):
        #     for y in range(self.n):
        #         if self.visitAtlantic[x][y] and self.visitPacific[x][y]:
        #             self.res.append([x,y])
        #
        # print self.res
        # return self.res



    def inArea(self,x,y):
        return x >= 0 and x < self.m and y >= 0 and y < self.n


    def toPacific(self,matrix):
        for item in self.PacificStart:
            x = item[0]
            y = item[1]

            if not self.visitPacific[x][y]:
                self.dfsToPacific(matrix, x, y)

    def dfsToPacific(self,matrix,x,y):

        self.visitPacific[x][y] = True

        for item in self.derecToPacific:
            newX = x + item[0]
            newY = y + item[1]

            if self.inArea(newX,newY) and not self.visitPacific[newX][newY] and matrix[newX][newY] >= matrix[x][y]:
                self.dfsToPacific(matrix,newX,newY)
        return



    def toAtlantic(self,matrix):
        for item in self.AtlanticStart:
            x = item[0]
            y = item[1]

            if not self.visitAtlantic[x][y]:
                self.dfsToAtlantic(matrix, x, y)

    def dfsToAtlantic(self, matrix, x, y):

        self.visitAtlantic[x][y] = True

        for item in self.derecToAtlantic:
            newX = x + item[0]
            newY = y + item[1]

            if self.inArea(newX, newY) and not self.visitAtlantic[newX][newY] and matrix[newX][newY] >= matrix[x][y]:
                self.dfsToAtlantic(matrix, newX, newY)
        return

# 第一版代码错误，应该是4个方向，而不是另个方向

class Solution2(object):
    def pacificAtlantic(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[List[int]]
        """

        self.res = []

        if not matrix:
            return self.res


        self.m = len(matrix)        self.n = len(matrix[0])        self.derection= [[-1,0],[0,1],[1,0],[0,-1]]        self.visitPacific = [[False for i in range(self.n)] for i in range(self.m)]        self.visitAtlantic = [[False for i in range(self.n)] for i in range(self.m)]        self.PacificStart = []        self.AtlanticStart = []        for y in range(self.n):            self.PacificStart.append([0,y])            self.AtlanticStart.append([self.m-1,y])        for x in range(self.m):            self.PacificStart.append([x,0])            self.AtlanticStart.append([x,self.n-1])        # for x in range(self.m):        #     self.AtlanticStart.append([x, self.n - 1])        # for y in range(self.n):        #     self.AtlanticStart.append([self.m-1, y])        # test        self.toPacific(matrix)        print  self.visitPacific        self.toAtlantic(matrix)        print  self.visitAtlantic        # self.toPacific(matrix)        # self.toAtlantic(matrix)        #        # for x in range(self.m):        #     for y in range(self.n):        #         if self.visitAtlantic[x][y] and self.visitPacific[x][y]:        #             self.res.append([x,y])        #        # print self.res        # return self.res    def inArea(self,x,y):        return x >= 0 and x < self.m and y >= 0 and y < self.n    def toPacific(self,matrix):        for item in self.PacificStart:            x = item[0]            y = item[1]            if not self.visitPacific[x][y]:                self.dfsToPacific(matrix, x, y)    def dfsToPacific(self,matrix,x,y):        self.visitPacific[x][y] = True        for item in self.derection:            newX = x + item[0]            newY = y + item[1]            if self.inArea(newX,newY) and not self.visitPacific[newX][newY] and matrix[newX][newY] >= matrix[x][y]:                self.dfsToPacific(matrix,newX,newY)        return    def toAtlantic(self,matrix):        for item in self.AtlanticStart:            x = item[0]            y = item[1]            if not self.visitAtlantic[x][y]:                self.dfsToAtlantic(matrix, x, y)    def dfsToAtlantic(self, matrix, x, y):        self.visitAtlantic[x][y] = True        for item in self.derection:            newX = x + item[0]            newY = y + item[1]            if self.inArea(newX, newY) and not self.visitAtlantic[newX][newY] and matrix[newX][newY] >= matrix[x][y]:                self.dfsToAtlantic(matrix, newX, newY)        returns = Solution2()# mat = [#     [1,2,2,3,5],#     [3,2,3,4,4],#     [2,4,5,3,1],#     [6,7,1,4,5],#     [5,1,1,2,4]# ]# mat = [#     [1,2],#     [4,3]## ]mat = [    [1,2,3],    [8,9,4],    [7,6,5]]s.pacificAtlantic(mat)