解题思路:
先排序,负值略过,重复略过,按1至N对比,如没有则返回
'''
#
# return the min number
# @param arr int整型一维数组 the array
# @return int整型
#
class Solution:
    def minNumberdisappered(self , arr ):
        # write code here
        L = sorted(arr)
        L.append(L[-1]+1)
        #print(L)
        k = 1
        for i in range(len(L)-1):
            #print('i=',i,'k=',k)
            if L[i]<0:
                continue
            if L[i]==L[i+1]:
                continue
            if L[i] != k:
                break
            else:
                k += 1
        #print('k=',k)
        return k

#print(Solution().minNumberdisappered([-1,1,3,2,4]))