# LeetCode OJ 219. 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 difference between i and j is at most k.

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Tags: Array, Hash Table
Similar Problems: Contains Duplicate, Contains Duplicate III

``````class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int size_nums = nums.size();
if(size_nums <= 1) return false;
//if(size_nums - 1  k)
int diff = 0;

bool flag = false;
bool result = false;
set<int> mp1;
set<int>::iterator iter1;
for(int i = 0; i < size_nums; i++)
{
mp1.insert(nums[i]);
}

vector<vector<int>> sequence1;
vector<int> temp;
for(iter1 = mp1.begin(); iter1 != mp1.end(); iter1++)
{
temp.clear();
for(int j = 0; j < size_nums; j++)
{
if(nums[j] == *iter1)
temp.push_back(j);
}
sequence1.push_back(temp);
}

for(int i = 0; i < sequence1.size(); i++)
{
temp.clear();
temp = sequence1[i];
int size_temp = temp.size();
if(size_temp == 1) continue;

int diff2 = temp[1] - temp[0];
for(int j = 1; j < size_temp; j++)
{
if((temp[j] - temp[j-1]) < diff2)
{
diff2 = (temp[j] - temp[j-1]);
cout << diff2;
}
}

if(diff == 0) diff = diff2;
cout << " " << diff << endl;
if(diff2 < diff) diff = diff2;
cout << " " << diff << endl;
}
return (diff != 0) && (diff <= k);

}
};
``````

``````class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int size_nums = nums.size();
if(size_nums <= 1) return false;

unordered_map<int, int> mp1;
for (int i = 0; i < nums.size(); ++i) {
//扫描一遍数组，如果首次出现，将元素和位序加入map
//如果找到了（即重复出现），比较当前位序与该元素上次出现时的位序，若差不大于k，返回true
//若不满足，将map中该重复数字的值更新为当前位序
//算法时间复杂度：O(n)，其中map的find函数为O(logn)
if (mp1.find(nums[i]) != mp1.end() && i - mp1[nums[i]] <= k)
{
cout << i << " " << mp1[nums[i]] << endl;
return true;
}
else mp1[nums[i]] = i;
}
return false;

}
};
``````