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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4. using namespace std;
  5. #define int long long
  6. namespace
  7. {
  8.  
  9.     int N, M;
  10.     vector<int> A;
  11.     vector<int> prefixSum;
  12.     vector<int> moddedPrefixBIT;
  13.     int ans;
  14.  
  15.     void inputInfo();
  16.  
  17.     void findAns();
  18.  
  19.     void addToBit(int x, int value);
  20.     int query(int x);
  21.  
  22.     void outputAns();
  23. }
  24.  
  25. int32_t main()
  26. {
  27.     while (cin >> N >> M)
  28.     {
  29.         inputInfo();
  30.         findAns();
  31.         outputAns();
  32.     }
  33. }
  34.  
  35. namespace
  36. {
  37.     void inputInfo()
  38.     {
  39.         A.clear(), A.resize(N + 1);
  40.         for (int i = 1; i <= N; i++)
  41.         {
  42.             cin >> A[i];
  43.         }
  44.     }
  45.  
  46.     void findAns()
  47.     {
  48.         // Mod all values in initial array
  49.         for (int i = 1; i <= N; i++)
  50.         {
  51.             A[i] %= M;
  52.         }
  53.  
  54.         // Prefix sum
  55.         prefixSum.clear(), prefixSum.resize(N + 1);
  56.         prefixSum[0] = 0;
  57.         for (int i = 1; i <= N; i++)
  58.         {
  59.             prefixSum[i] = prefixSum[i - 1] + A[i];
  60.         }
  61.  
  62.         // Calculate total sum
  63.         int totalSum = 0;
  64.         for (int i = 1; i <= N; i++)
  65.         {
  66.             totalSum += prefixSum[i] % M;
  67.         }
  68.  
  69.         // Create Fenwick tree
  70.         moddedPrefixBIT.clear(), moddedPrefixBIT.resize(M + 1);
  71.         for (int i = 1; i <= N; i++)
  72.         {
  73.             addToBit(prefixSum[i] % M + 1, 1);
  74.         }
  75.  
  76.         // Calculate answer
  77.         ans = 0;
  78.         int reducedSum = 0;
  79.         int termsCount = N;
  80.         for (int i = 1; i <= N; i++)
  81.         {
  82.             // Count # of modded prefix sum < reducedSum
  83.             int negativeReducedCount = query(reducedSum);
  84.  
  85.             // Update answer
  86.             ans += totalSum;
  87.             ans -= reducedSum * termsCount;
  88.             ans += negativeReducedCount * M;
  89.  
  90.             // Update state
  91.             totalSum -= prefixSum[i] % M;
  92.             reducedSum += A[i];
  93.             reducedSum %= M;
  94.             termsCount--;
  95.             addToBit(prefixSum[i] % M + 1, -1);
  96.         }
  97.     }
  98.  
  99.     void addToBit(int x, int value)
  100.     {
  101.         for (int i = x; i <= M; i += (i & (-i)))
  102.         {
  103.             moddedPrefixBIT[i] += value;
  104.         }
  105.     }
  106.  
  107.     int query(int x)
  108.     {
  109.         int value = 0;
  110.         for (int i = x; i > 0; i -= (i & (-i)))
  111.         {
  112.             value += moddedPrefixBIT[i];
  113.         }
  114.         return value;
  115.     }
  116.  
  117.     void outputAns()
  118.     {
  119.         cout << ans << '\n';
  120.     }
  121. }
  122.  
Success #stdin #stdout 0.01s 5272KB
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https://ideone.com/C3F9xl
language:
C++14 (gcc 8.3)
created:
18 days ago
visibility:
secret

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