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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. typedef long long ll;
  4. const int MOD = 1e9 + 7;
  5. const int N = 1e5 + 5;
  6.  
  7.  
  8. int n, w;
  9. int a[105];
  10. ll dp[N], prfx[2][N];
  11.  
  12.  
  13. ll pfx(int u, int v, int x)
  14. {
  15.     return ((prfx[x][v + 1] % MOD) - (prfx[x][u] % MOD) + MOD) % MOD;
  16. }
  17.  
  18.  
  19. int main() {
  20.     ios_base::sync_with_stdio(false); cin.tie(NULL);
  21.  
  22.     cin >> n >> w;
  23.  
  24.     for (int i = 1; i <= n; i++) cin >> a[i];
  25.  
  26.     memset(dp, 0, sizeof(dp));
  27.     for (int i = 1; i <= w + 1; i++) prfx[0][i] = 1;
  28.     prfx[0][0] = 0; prfx[1][0] = 0; prfx[1][1] = 1;
  29.     dp[0] = 1;
  30.  
  31.     for (int i = 1; i <= n ; i++)
  32.     {
  33.         int y, x; y = i % 2; x = 1 - y;
  34.         for (int j = 1; j <= w; j++)
  35.         {
  36.             dp[j] = pfx(max(0, j - a[i]), j, x);
  37.             prfx[y][j + 1] = ((prfx[y][j] % MOD) + dp[j]) % MOD;
  38.         }
  39.     }
  40.  
  41.     cout << dp[w];
  42.  
  43.     return 0;
  44. }
  45.  
Success #stdin #stdout 0.01s 5300KB
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https://ideone.com/ZjBQS0
language:
C++14 (gcc 8.3)
created:
8 days ago
visibility:
public

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