Create 2537.Count-the-Number-of-Good-Subarrays.cpp

Author: wisdompeak

Two_Pointers/2537.Count-the-Number-of-Good-Subarrays/2537.Count-the-Number-of-Good-Subarrays.cpp

@@ -0,0 +1,38 @@
+using LL = long long;
+class Solution {
+ LL total = 0;
+ LL ret = 0;
+public:
+ long long countGood(vector<int>& nums, int k) 
+ {
+ int n = nums.size();
+ int j = 0;
+ unordered_map<int,int>count;
+ 
+ for (int i=0; i<n; i++)
+ {
+ while (j<n && total < k)
+ { 
+ total += diff(count, nums[j], 1);
+ count[nums[j]]++;
+ j++;
+ }
+ if (total >= k)
+ ret += n-j+1;
+ 
+ total += diff(count, nums[i], -1);
+ count[nums[i]]--;
+ }
+ 
+ return ret; 
+ }
+ 
+ LL diff(unordered_map<int,int>&count, int num, int d)
+ {
+ LL m = count[num];
+ LL old = m*(m-1)/2;
+ m += d;
+ LL now = m*(m-1)/2;
+ return now - old;
+ }
+};