递归和回溯_leetcode46-经典的排列去重

#coding=utf-8
class Solution1(object):
    def permuteUnique(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        self.res = []

        nums.sort()
        length = len(nums)

        self.used = [False for i in range(length)]

        self.generatePermute(nums,0,[])

        if 0:
            print "lx"
        if 1:
            print "dd"


        print self.res
        return self.res

    # 去重思路：同一个位置的值不能出现两次，即下一个进入该位置的值，不能
    # 和该位置刚出栈的值相同

    def generatePermute(self,nums,index,p):

        if index == len(nums):
            self.res.append(p[0:])
            return

        old = None

        for i in range(len(nums)):

            # if old:
            #     if not self.used[i] and nums[i] != old:
            #         p.append(nums[i])
            #         self.used[i] = True
            #         self.generatePermute(nums,index+1 ,p)
            #         self.used[i] = False
            #         old = p.pop()
            # else:
            #     if not self.used[i]:
            #         p.append(nums[i])
            #         self.used[i] = True
            #         self.generatePermute(nums,index+1 ,p)
            #         self.used[i] = False
            #         old = p.pop()

            #if old != None:
            if old:     # 这句有坑 原因在于 if 0 是假的
                if self.used[i] == False and old != nums[i]:
                    p.append(nums[i])
                    self.used[i] = True
                    self.generatePermute(nums, index + 1, p)
                    self.used[i] = False
                    old = p.pop()

            else:
                if self.used[i] == False:
                    p.append(nums[i])
                    self.used[i] = True
                    self.generatePermute(nums, index + 1, p)
                    self.used[i] = False
                    old = p.pop()



# solution1 是错误的
class Solution2(object):
    def permuteUnique(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        self.res = []

        nums.sort()
        self.visit = [0 for i in range(len(nums))]
        self.old = None
        for i in range(len(nums)):
            if self.old == None:
                self.generatePermute(nums,i,0,[])
                self.old = nums[i]
            else:
                 if nums[i] == self.old:
                     continue
                 else:
                     self.generatePermute(nums, i, 0, [])
                     self.old = nums[i]


        print self.res

    def generatePermute(self, nums,start,index, p):

        self.visit[start] = 1
        p.append(nums[start])

        self.getPermute(nums,index+1,p)

        self.visit[start] = 0
        p.pop()


    def getPermute(self, nums, index, p):

        if index == len(nums):
            self.res.append(p[0:])
            return

        for i in range(len(nums)):

            if self.visit[i] == 0:
                p.append(nums[i])
                self.visit[i] = 1
                self.getPermute(nums, index + 1, p)
                self.visit[i] = 0
                self.old = p.pop()






# Solution1 的思路是正确的
# Solution2 是错的
class Solution3(object):
    def permuteUnique(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        self.res = []

        nums.sort()
        self.visit = [0 for i in range(len(nums))]        self.old = None        self.generatePermute(nums,0,[])        print self.res    def generatePermute(self, nums,index, p):        if index == len(nums):            self.res.append(p[0:])        old = None        for i in range(len(nums)):            if  old == None:                if self.visit[i] == 0:                    p.append(nums[i])                    self.visit[i] = 1                    self.generatePermute(nums,index+1,p)                    self.visit[i] = 0                    old = p.pop()            else:                if self.visit[i] == 0 and nums[i] != old:                    p.append(nums[i])                    self.visit[i] = 1                    self.generatePermute(nums,index+1 ,p)                    self.visit[i] = 0                    old = p.pop()s = Solution1()n = [1,1,2]n1 = [0,1,0,0,9]n2 = [0,1,0,0]n3 = [0,0,1]n4 = [1,2,3]n5 = [2,3,2]n6 = [1,1]s.permuteUnique(n6)