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  1. #include<bits/stdc++.h>
  2. #define MOD 998244353
  3. #define x(p) p.second.first
  4. #define y(p) p.second.second
  5. #define sqeud(a) (x(a)*x(a)+y(a)*y(a))
  6.  
  7. using namespace std;
  8.  
  9. typedef long long ll;
  10. typedef pair<ll, pair<int, int>> p3;
  11.  
  12. ll modpow(ll a, ll n) {
  13.     if(n == 0 or a == 1) return 1;
  14.     else if(n == 1) return a;
  15.  
  16.     if(n&1) return (a * modpow(a, n-1)) % MOD;
  17.  
  18.     ll temp = modpow(a, n / 2);
  19.     return (temp*temp) % MOD;
  20. }
  21.  
  22. ll modinv(ll a) {
  23.     return modpow(a, MOD-2);
  24. }
  25.  
  26.  
  27.  
  28. int main() {
  29.     ios::sync_with_stdio(false);
  30.  
  31.  
  32.     #ifdef DBG
  33.     freopen("in", "r", stdin);
  34.     #endif
  35.  
  36.     int n, m, r, c;
  37.     cin>>n>>m;
  38.  
  39.     vector<p3> arr(n*m);
  40.  
  41.     for(int i = 0; i < n; i++) {
  42.         for(int j = 0; j < m; j++) {
  43.             int ind = i*m + j;
  44.             cin>>arr[ind].first;
  45.             arr[ind].second = {i + 1, j + 1};
  46.         }
  47.     }
  48.     cin>>r>>c;
  49.  
  50.     sort(arr.begin(), arr.end());
  51.  
  52.     vector<ll> sqsum(n*m, 0);
  53.     vector<ll> xsum(n*m, 0);
  54.     vector<ll> ysum(n*m, 0);
  55.     vector<ll> vsum(n*m, 0);
  56.     // int i;
  57.  
  58.     ll v;
  59.  
  60.     for(int i = 0; i < n*m; i++) {
  61.         if(i == 0) {
  62.             sqsum[i] = sqeud(arr[i]);
  63.             xsum[i] = x(arr[i]);
  64.             ysum[i] = y(arr[i]);
  65.         } else {
  66.             sqsum[i] = (sqsum[i-1] + sqeud(arr[i]))%MOD;
  67.             xsum[i] = xsum[i-1] + x(arr[i]);
  68.             ysum[i] = ysum[i-1] + y(arr[i]);
  69.         }
  70.  
  71.         if(x(arr[i]) == r and y(arr[i]) == c) {
  72.             v = arr[i].first;
  73.         }
  74.     }
  75.  
  76.     ll ans = 0ll;
  77.  
  78.     for(int i = n*m - 1; i > 0; i--) {
  79.         if(arr[i].first > v) continue;
  80.         else if(arr[i].first == v and (x(arr[i]) != r or y(arr[i]) != c)) continue;
  81.  
  82.         p3 value = {arr[i].first, {-1, -1}};
  83.         int ind = lower_bound(arr.begin(), arr.end(), value) - arr.begin();
  84.         if(ind == 0) {
  85.             break;
  86.         }
  87.         ll count = ind;
  88.         ind--;
  89.         ll count_inv = modinv(count);
  90.         ll val = (count*sqeud(arr[i]))%MOD;
  91.  
  92.         val = (val + sqsum[ind])%MOD;
  93.         val -= (2*x(arr[i])*xsum[ind]);
  94.         val -= (2*y(arr[i])*ysum[ind]);
  95.         while(val < 0) {
  96.             val += MOD;
  97.         }
  98.  
  99.         val = (val * count_inv) % MOD;
  100.         ans = (ans + val) % MOD;
  101.     }
  102.     cout<<ans;
  103.     return 0;
  104. }
Success #stdin #stdout 0s 15240KB
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https://ideone.com/Zn0ail
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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