# 1248. Count Number of Nice Subarrays | LeetCode Solution

## 1248. Count Number of Nice Subarrays | LeetCode Solution

Given an array of integers `nums` and an integer `k`. A continuous subarray is called nice if there are `k` odd numbers on it.

Return the number of nice sub-arrays.

Example 1:

```Input: nums = [1,1,2,1,1], k = 3
Output: 2
Explanation: The only sub-arrays with 3 odd numbers are [1,1,2,1] and [1,2,1,1].
```

Example 2:

```Input: nums = [2,4,6], k = 1
Output: 0
Explanation: There is no odd numbers in the array.
```

Example 3:

```Input: nums = [2,2,2,1,2,2,1,2,2,2], k = 2
Output: 16
```

Constraints:

• `1 <= nums.length <= 50000`
• `1 <= nums[i] <= 10^5`
• `1 <= k <= nums.length`

class Solution {
public:
int numberOfSubarrays(vector<int>& nums, int k) {
for(int i=0; i<nums.size(); i++){
if(nums[i]%2==0)nums[i]=0;
else nums[i]=1;
}

unordered_map<int,int>mymap;

int sum=0,ans=0;
mymap[sum]=1;
for(int i=0; i<nums.size(); i++){
sum+=nums[i];
auto it=mymap.find(sum-k);
if(it!=mymap.end())ans+=mymap[sum-k];
mymap[sum]++;
}
return ans;
}
};