#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
long long n, pref[300002], wyn, dp[300002], a[300002], b;
void brt(int id)
{
if (id >= n)
{
// cout << id << endl;
wyn++;
return;
}
long long sm = 0;
for (int i = id; i < n; ++i)
{
sm += a[i];
sm %= mod;
if (sm % 2 == 0)
{
// cout << id << " " << i << " " << sm << endl;
brt(i + 1);
}
}
}
int main()
{
scanf("%lld", &n);
if (n <= 3000)
{
for (int i = 0; i < n; ++i)
{
scanf("%lld", &a[i]);
}
brt(0);
printf("%lld", wyn);
}
else
{
for (int i = 0; i < n; ++i)
{
scanf("%lld", &b);
pref[i] = b;
if (i > 0)
pref[i] += pref[i - 1];
pref[i] %= mod;
// cout << pref[i] << endl;
}
// return 0;
long long p = 0, np = 0;
for (int i = 0; i < n; ++i)
{
if (pref[i] % 2 == 0)
{
dp[i] = p + 1;
dp[i] %= mod;
p += dp[i];
p %= mod;
// cout << p << " " << pref[i] << " " << i << endl;
}
}
printf("%lld", dp[n - 1]);
}
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | #include <bits/stdc++.h> using namespace std; #define mod 1000000007 long long n, pref[300002], wyn, dp[300002], a[300002], b; void brt(int id) { if (id >= n) { // cout << id << endl; wyn++; return; } long long sm = 0; for (int i = id; i < n; ++i) { sm += a[i]; sm %= mod; if (sm % 2 == 0) { // cout << id << " " << i << " " << sm << endl; brt(i + 1); } } } int main() { scanf("%lld", &n); if (n <= 3000) { for (int i = 0; i < n; ++i) { scanf("%lld", &a[i]); } brt(0); printf("%lld", wyn); } else { for (int i = 0; i < n; ++i) { scanf("%lld", &b); pref[i] = b; if (i > 0) pref[i] += pref[i - 1]; pref[i] %= mod; // cout << pref[i] << endl; } // return 0; long long p = 0, np = 0; for (int i = 0; i < n; ++i) { if (pref[i] % 2 == 0) { dp[i] = p + 1; dp[i] %= mod; p += dp[i]; p %= mod; // cout << p << " " << pref[i] << " " << i << endl; } } printf("%lld", dp[n - 1]); } } |
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