leetcode_Contains Duplicate II_easy

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.

方法很简单：和之前的那道题目类似，也是用map。

class Solution {
public:
    bool containsNearbyDuplicate(vector<int>& nums, int k) {
        map<int, int> kvmap;
        for(int i=0; i<nums.size(); i++)
        {
            map<int, int>::iterator tmp_iter=kvmap.find(nums[i]);
            if(tmp_iter==kvmap.end())//之前没有这样的数字,此数字首次出现
                kvmap[nums[i]]=i;
            else
                if( i-kvmap[nums[i]]<=k)//出现了之前已经出现过的数字
                    return true;
                else
                    kvmap[nums[i]]=i;//更新最近出现的位置
        }
        return false;
    }
};