Contains Duplicate II:
Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.
Example 1:
Input: nums = [1,2,3,1], k = 3
Output: true
Example 2:
Input: nums = [1,0,1,1], k = 1
Output: true
Example 3:
Input: nums = [1,2,3,1,2,3], k = 2
Output: false
Solution:
#include <iostream>
#include <vector>
#include <unordered_set>
using namespace std;
// 时间复杂度: o(n)
// 空间复杂度: o(k)
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
unordered_set<int> record;
for( int i = 0; i < nums.size(); i++ ){
if( record.find( nums[i] ) != record.end() )
return true;
record.insert( nums[i] );
// 保持record中最多有k个元素
if( record.size() == k + 1 )
record.erase( nums[i-k] );
}
return false;
}
};
总结: 这道题用了滑动窗口+查找表的思路。用举例子的方法可以更好的理解这个解题方法。