#include <bits/stdc++.h> using namespace std; using LL = long long; LL MOD = 1e9+7; const LL MAX = 300007; LL arr[MAX]; LL prefsum[MAX]; LL DP2[MAX]; int main() { ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); int n; cin >> n; LL sum = 0; bool b1 = true; for (int i = 1; i <= n; ++i) { int a; cin >> a; sum += a; arr[i] = a; prefsum[i] = prefsum[i - 1] + a; if (a > 100) { b1 = false; } } if (b1) { LL cnt = 0; if (prefsum[n] % 2 != 0) { cout << "0\n"; return 0; } LL res = 1; for (int i = 1; i < n; ++i) { if (prefsum[i] % 2 == 0) { res = (res * 2) % MOD; } } cout << res << "\n"; return 0; } else if (n <= 3000) { auto ok = [&](int a, int b) { return ((prefsum[b] - prefsum[a - 1]) % MOD) % 2 == 0; }; DP2[0] = 1; for (int i = 1; i <= n; ++i) { for (int j = 1; j <= i; ++j) { if (ok(j, i)) DP2[i] = (DP2[i] + DP2[j - 1]) % MOD; } } cout << DP2[n] << "\n"; return 0; } return 0; }
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 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 | #include <bits/stdc++.h> using namespace std; using LL = long long; LL MOD = 1e9+7; const LL MAX = 300007; LL arr[MAX]; LL prefsum[MAX]; LL DP2[MAX]; int main() { ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); int n; cin >> n; LL sum = 0; bool b1 = true; for (int i = 1; i <= n; ++i) { int a; cin >> a; sum += a; arr[i] = a; prefsum[i] = prefsum[i - 1] + a; if (a > 100) { b1 = false; } } if (b1) { LL cnt = 0; if (prefsum[n] % 2 != 0) { cout << "0\n"; return 0; } LL res = 1; for (int i = 1; i < n; ++i) { if (prefsum[i] % 2 == 0) { res = (res * 2) % MOD; } } cout << res << "\n"; return 0; } else if (n <= 3000) { auto ok = [&](int a, int b) { return ((prefsum[b] - prefsum[a - 1]) % MOD) % 2 == 0; }; DP2[0] = 1; for (int i = 1; i <= n; ++i) { for (int j = 1; j <= i; ++j) { if (ok(j, i)) DP2[i] = (DP2[i] + DP2[j - 1]) % MOD; } } cout << DP2[n] << "\n"; return 0; } return 0; } |