LeetCode#219 Contains Duplicate II

Problem Definition:

　　Given an array of integers and an integer k, find out whether there there are two

　　distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.

 

Solution 1:  O(n^2)  (报超时)

def containsNearbyDuplicate(nums, k):
        n=len(nums)
        if n*k==0:
            return False
        i=0
        while i<n-1:
            j=1
            while j<=k:
                if (i+j)>(n-1):
                    break
                if nums[i]==nums[i+j]:
                    return True
                else:
                    j+=1
            i+=1
        return False

 

Solution 2: 以空间换时间，遍历过程中把数组内的值和值的下标以键值对的形成保存在字典中( dict )，字典查询的时间复杂度是O(1)。

 1 def containsNearbyDuplicate(self, nums, k):
 2         n = len(nums)
 3         if n*k==0:
 4             return False
 5         d = {}
 6         for i in range(n):
 7             if nums[i] not in d:
 8                 d[nums[i]] = i
 9             else:
10                 diff = abs(d[nums[i]]-i)
11                 if diff <= k:
12                     return True
13                 else:
14                     d[nums[i]] = i
15         return False