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Candies.cpp
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Candies.cpp
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// Author : Syed Mujtaba
// Seek knowledge from the Cradle to the Grave !!
// https://www.linkedin.com/in/syed-mujtaba-064a5016a
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fast_io ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define mod ((int)(1e9 + 7))
signed main()
{
fast_io
int n, k;
cin >> n >> k;
int a[n + 1];
int dp[n + 1][k + 1];
vector < int > psa(n + 1, 0);
for(int i = 1; i <= n; i++)
cin >> a[i];
for(int i = 1; i <= n; i++)
{
psa[i] = a[i] + psa[i - 1];
}
vector < int > ps[n + 4];
for(int i = 0; i <= n; i++)
{
ps[i].resize(k + 4);
for(int j = 0; j <= k; j++)
ps[i][j] = 0;
}
for(int i = 0; i <= k; i++)
{
if(i <= a[1])
dp[1][i] = 1;
else
dp[1][i] = 0;
ps[1][i+1] = (ps[1][i]%mod + dp[1][i]%mod)%mod;
}
for(int i = 2; i <= n; i++)
{
dp[i][0] = 1;
ps[i][1] = 1;
for(int j = 1; j <= k; j++)
{
dp[i][j] = 0;
dp[i][j] = (ps[i - 1][j + 1]%mod - ps[i - 1][max(0LL, j - a[i])]%mod + mod)%mod;
ps[i][j + 1] = (ps[i][j]%mod + dp[i][j]%mod)%mod;
}
}
cout << dp[n][k] << endl;
}