Create 2031.Count-Subarrays-With-More-Ones-Than-Zeros.cpp

Author: wisdompeak

Segment_Tree/2031.Count-Subarrays-With-More-Ones-Than-Zeros/2031.Count-Subarrays-With-More-Ones-Than-Zeros.cpp

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+const int MAX_N = 200003;
+using LL = long long;
+
+class Solution { 
+ int OFFSET = 100001;
+ long long bitArr[MAX_N];
+ long long nums[MAX_N]; // Note: nums is 1-index
+ long long M = 1e9+7;
+
+ // increase nums[i] by delta (1-index)
+ void updateDelta(int i, long long delta) {
+ int idx = i;
+ while (idx <= MAX_N)
+ {
+ bitArr[idx]+=delta;
+ bitArr[idx] %= M;
+ idx+=idx&(-idx);
+ }
+ }
+
+ // sum of a range nums[1:j] inclusively, 1-index
+ long long queryPreSum(int idx){
+ long long result = 0;
+ while (idx){
+ result += bitArr[idx];
+ result %= M;
+ idx-=idx&(-idx);
+ }
+ return result;
+ }
+
+ // sum of a range nums[i:j] inclusively
+ long long sumRange(int i, int j) { 
+ return queryPreSum(j)-queryPreSum(i-1);
+ }
+ 
+public:
+ int subarraysWithMoreZerosThanOnes(vector<int>& nums) 
+ {
+ cout<<nums.size()<<endl;
+ int diff = 0;
+ LL ret = 0;
+ updateDelta(0+OFFSET, 1);
+ 
+ for (int i=0; i<nums.size(); i++)
+ {
+ if (nums[i]==1) diff++;
+ else diff--;
+ 
+ ret = (ret + queryPreSum(diff-1+OFFSET)) % M; 
+ updateDelta(diff+OFFSET, 1);
+ } 
+ return ret; 
+ }
+};