#include <bits/stdc++.h> using namespace std; #define rep(i, n) for(int i = 0; i < n; i++) #define pb push_back #define debug(x) cout << #x << " " << x << endl #define all(x) x.begin(),x.end() #define ll long long #define vi vector<int> #define vvi vector<vi> #define vvvi vector<vvi> #define vll vector<ll> #define vvll vector<vll> #define ld long double #define ull unsigned long long #define vull vector<ull> #define fi first #define se second #define PII pair<int,int> #define vPII vector<PII> #define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());} #define int128 __int128 ll mod = 1e9+7; namespace modop { ll madd(ll a, ll b) { return (a + b) % mod; } ll msub(ll a, ll b) { return (((a - b) % mod) + mod) % mod; } ll mmul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod; } ll mpow(ll base, ll exp) { ll res = 1; while (exp) { if (exp % 2 == 1){ res = (res * base) % mod; } exp >>= 1; base = (base * base) % mod; } return res; } ll minv(ll base) { return mpow(base, mod - 2); } ll mdiv(ll a, ll b) { return mmul(a, minv(b)); } const ll FACTORIAL_SIZE = 1.1e6; ll fact[FACTORIAL_SIZE], ifact[FACTORIAL_SIZE]; bool __factorials_generated__ = 0; void gen_factorial(ll n) { __factorials_generated__ = 1; fact[0] = fact[1] = ifact[0] = ifact[1] = 1; for (ll i = 2; i <= n; i++) { fact[i] = (i * fact[i - 1]) % mod; } ifact[n] = minv(fact[n]); for (ll i = n - 1; i >= 2; i--) { ifact[i] = ((i + 1) * ifact[i + 1]) % mod; } } ll nck(ll n, ll k) { if (!__factorials_generated__) { cerr << "Call gen_factorial you dope" << endl; exit(1); } if (k < 0 || n < k) return 0; ll den = (ifact[k] * ifact[n - k]) % mod; return (den * fact[n]) % mod; } } using namespace modop; struct sum_t { long long val; static const long long null_v = 0; sum_t(): val(0) {} sum_t(long long v): val(v) {} sum_t op(sum_t& other) { return sum_t(madd(val,other.val)); } sum_t lazy_op(sum_t& v, int size) { return sum_t(madd(val, v.val * size)); } }; template <typename num_t> struct segtree { int n, depth; vector<num_t> tree, lazy; void init(int s, long long* arr) { n = s; tree = vector<num_t>(4 * s, 0); lazy = vector<num_t>(4 * s, 0); init(0, 0, n - 1, arr); } num_t init(int i, int l, int r, long long* arr) { if (l == r) return tree[i] = arr[l]; int mid = (l + r) / 2; num_t a = init(2 * i + 1, l, mid, arr), b = init(2 * i + 2, mid + 1, r, arr); return tree[i] = a.op(b); } void update(int l, int r, num_t v) { if (l > r) return; update(0, 0, n - 1, l, r, v); } num_t update(int i, int tl, int tr, int ql, int qr, num_t v) { eval_lazy(i, tl, tr); if (tr < ql || qr < tl) return tree[i]; if (ql <= tl && tr <= qr) { lazy[i] = lazy[i].val + v.val; eval_lazy(i, tl, tr); return tree[i]; } int mid = (tl + tr) / 2; num_t a = update(2 * i + 1, tl, mid, ql, qr, v), b = update(2 * i + 2, mid + 1, tr, ql, qr, v); return tree[i] = a.op(b); } num_t query(int l, int r) { if (l > r) return num_t::null_v; return query(0, 0, n-1, l, r); } num_t query(int i, int tl, int tr, int ql, int qr) { eval_lazy(i, tl, tr); if (ql <= tl && tr <= qr) return tree[i]; if (tr < ql || qr < tl) return num_t::null_v; int mid = (tl + tr) / 2; num_t a = query(2 * i + 1, tl, mid, ql, qr), b = query(2 * i + 2, mid + 1, tr, ql, qr); return a.op(b); } void eval_lazy(int i, int l, int r) { tree[i] = tree[i].lazy_op(lazy[i], (r - l + 1)); if (l != r) { lazy[i * 2 + 1] = lazy[i].val + lazy[i * 2 + 1].val; lazy[i * 2 + 2] = lazy[i].val + lazy[i * 2 + 2].val; } lazy[i] = num_t(); } }; segtree<sum_t> st0,st1; map<ll,int> mapka0, mapka1; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); // cout << setprecision(16) << fixed; // freopen("input.txt", "r", stdin); // freopen("output.txt", "w", stdout); int tt = 1; // cin >> tt; while(tt--) { ll n; cin >> n; ll suma2 = 0; vll a(n+1); a[0] = 0; rep(i,n){ cin >> a[i+1]; suma2 += a[i+1]; } if(suma2 < mod){ ll suma = 0; ll cnt = 0; for(int i = 1; i < n; i++){ suma += a[i]; if(suma%2==0) cnt++; } suma += a[n]; cout << ((suma%2 == 0) ? mpow(2ll,cnt) : 0); return 0; } ll pref[n+1]; pref[0] = 0; for(int i = 1; i <= n; i++){ pref[i] = madd(a[i],pref[i-1]); } vector<ll> parz,niep; int ncnt = 0, pcnt = 0; rep(i,n+1){ if(pref[i]&1){ niep.pb(pref[i]); }else{ parz.pb(pref[i]); } } sort(all(niep)); sort(all(parz)); ll do1[niep.size()], do0[parz.size()]; rep(i,niep.size()) do1[i] = 0; rep(i,parz.size()) do0[i] = 0; do0[0] = 1; st1.init(niep.size(),do1); st0.init(parz.size(),do0); ll dp[n+1]; dp[0] = 1; int nsiz = niep.size(); int psiz = parz.size(); for(int i = 1; i <= n; i++){ dp[i] = 0; if(pref[i]&1){ auto dok = upper_bound(all(niep),pref[i]); if(dok != niep.begin()){ dok--; dp[i] = madd(dp[i],st1.query(0,dok-niep.begin()).val); } dok = lower_bound(all(parz),pref[i]); if(dok != parz.end()){ dp[i] = madd(dp[i],st0.query(dok-parz.begin(),psiz).val); } int pom3 = lower_bound(all(niep),pref[i]) - niep.begin(); st1.update(pom3,pom3,dp[i]); }else{ auto dok = upper_bound(all(parz),pref[i]); if(dok != parz.begin()){ dok--; dp[i] = madd(dp[i],st0.query(0,dok-parz.begin()).val); } dok = lower_bound(all(niep),pref[i]); if(dok != niep.end()){ dp[i] = madd(dp[i],st1.query(dok-niep.begin(),nsiz).val); } int pom3 = lower_bound(all(parz),pref[i]) - parz.begin(); st0.update(pom3,pom3,dp[i]); } } cout << dp[n]; } }
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 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 | #include <bits/stdc++.h> using namespace std; #define rep(i, n) for(int i = 0; i < n; i++) #define pb push_back #define debug(x) cout << #x << " " << x << endl #define all(x) x.begin(),x.end() #define ll long long #define vi vector<int> #define vvi vector<vi> #define vvvi vector<vvi> #define vll vector<ll> #define vvll vector<vll> #define ld long double #define ull unsigned long long #define vull vector<ull> #define fi first #define se second #define PII pair<int,int> #define vPII vector<PII> #define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());} #define int128 __int128 ll mod = 1e9+7; namespace modop { ll madd(ll a, ll b) { return (a + b) % mod; } ll msub(ll a, ll b) { return (((a - b) % mod) + mod) % mod; } ll mmul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod; } ll mpow(ll base, ll exp) { ll res = 1; while (exp) { if (exp % 2 == 1){ res = (res * base) % mod; } exp >>= 1; base = (base * base) % mod; } return res; } ll minv(ll base) { return mpow(base, mod - 2); } ll mdiv(ll a, ll b) { return mmul(a, minv(b)); } const ll FACTORIAL_SIZE = 1.1e6; ll fact[FACTORIAL_SIZE], ifact[FACTORIAL_SIZE]; bool __factorials_generated__ = 0; void gen_factorial(ll n) { __factorials_generated__ = 1; fact[0] = fact[1] = ifact[0] = ifact[1] = 1; for (ll i = 2; i <= n; i++) { fact[i] = (i * fact[i - 1]) % mod; } ifact[n] = minv(fact[n]); for (ll i = n - 1; i >= 2; i--) { ifact[i] = ((i + 1) * ifact[i + 1]) % mod; } } ll nck(ll n, ll k) { if (!__factorials_generated__) { cerr << "Call gen_factorial you dope" << endl; exit(1); } if (k < 0 || n < k) return 0; ll den = (ifact[k] * ifact[n - k]) % mod; return (den * fact[n]) % mod; } } using namespace modop; struct sum_t { long long val; static const long long null_v = 0; sum_t(): val(0) {} sum_t(long long v): val(v) {} sum_t op(sum_t& other) { return sum_t(madd(val,other.val)); } sum_t lazy_op(sum_t& v, int size) { return sum_t(madd(val, v.val * size)); } }; template <typename num_t> struct segtree { int n, depth; vector<num_t> tree, lazy; void init(int s, long long* arr) { n = s; tree = vector<num_t>(4 * s, 0); lazy = vector<num_t>(4 * s, 0); init(0, 0, n - 1, arr); } num_t init(int i, int l, int r, long long* arr) { if (l == r) return tree[i] = arr[l]; int mid = (l + r) / 2; num_t a = init(2 * i + 1, l, mid, arr), b = init(2 * i + 2, mid + 1, r, arr); return tree[i] = a.op(b); } void update(int l, int r, num_t v) { if (l > r) return; update(0, 0, n - 1, l, r, v); } num_t update(int i, int tl, int tr, int ql, int qr, num_t v) { eval_lazy(i, tl, tr); if (tr < ql || qr < tl) return tree[i]; if (ql <= tl && tr <= qr) { lazy[i] = lazy[i].val + v.val; eval_lazy(i, tl, tr); return tree[i]; } int mid = (tl + tr) / 2; num_t a = update(2 * i + 1, tl, mid, ql, qr, v), b = update(2 * i + 2, mid + 1, tr, ql, qr, v); return tree[i] = a.op(b); } num_t query(int l, int r) { if (l > r) return num_t::null_v; return query(0, 0, n-1, l, r); } num_t query(int i, int tl, int tr, int ql, int qr) { eval_lazy(i, tl, tr); if (ql <= tl && tr <= qr) return tree[i]; if (tr < ql || qr < tl) return num_t::null_v; int mid = (tl + tr) / 2; num_t a = query(2 * i + 1, tl, mid, ql, qr), b = query(2 * i + 2, mid + 1, tr, ql, qr); return a.op(b); } void eval_lazy(int i, int l, int r) { tree[i] = tree[i].lazy_op(lazy[i], (r - l + 1)); if (l != r) { lazy[i * 2 + 1] = lazy[i].val + lazy[i * 2 + 1].val; lazy[i * 2 + 2] = lazy[i].val + lazy[i * 2 + 2].val; } lazy[i] = num_t(); } }; segtree<sum_t> st0,st1; map<ll,int> mapka0, mapka1; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); // cout << setprecision(16) << fixed; // freopen("input.txt", "r", stdin); // freopen("output.txt", "w", stdout); int tt = 1; // cin >> tt; while(tt--) { ll n; cin >> n; ll suma2 = 0; vll a(n+1); a[0] = 0; rep(i,n){ cin >> a[i+1]; suma2 += a[i+1]; } if(suma2 < mod){ ll suma = 0; ll cnt = 0; for(int i = 1; i < n; i++){ suma += a[i]; if(suma%2==0) cnt++; } suma += a[n]; cout << ((suma%2 == 0) ? mpow(2ll,cnt) : 0); return 0; } ll pref[n+1]; pref[0] = 0; for(int i = 1; i <= n; i++){ pref[i] = madd(a[i],pref[i-1]); } vector<ll> parz,niep; int ncnt = 0, pcnt = 0; rep(i,n+1){ if(pref[i]&1){ niep.pb(pref[i]); }else{ parz.pb(pref[i]); } } sort(all(niep)); sort(all(parz)); ll do1[niep.size()], do0[parz.size()]; rep(i,niep.size()) do1[i] = 0; rep(i,parz.size()) do0[i] = 0; do0[0] = 1; st1.init(niep.size(),do1); st0.init(parz.size(),do0); ll dp[n+1]; dp[0] = 1; int nsiz = niep.size(); int psiz = parz.size(); for(int i = 1; i <= n; i++){ dp[i] = 0; if(pref[i]&1){ auto dok = upper_bound(all(niep),pref[i]); if(dok != niep.begin()){ dok--; dp[i] = madd(dp[i],st1.query(0,dok-niep.begin()).val); } dok = lower_bound(all(parz),pref[i]); if(dok != parz.end()){ dp[i] = madd(dp[i],st0.query(dok-parz.begin(),psiz).val); } int pom3 = lower_bound(all(niep),pref[i]) - niep.begin(); st1.update(pom3,pom3,dp[i]); }else{ auto dok = upper_bound(all(parz),pref[i]); if(dok != parz.begin()){ dok--; dp[i] = madd(dp[i],st0.query(0,dok-parz.begin()).val); } dok = lower_bound(all(niep),pref[i]); if(dok != niep.end()){ dp[i] = madd(dp[i],st1.query(dok-niep.begin(),nsiz).val); } int pom3 = lower_bound(all(parz),pref[i]) - parz.begin(); st0.update(pom3,pom3,dp[i]); } } cout << dp[n]; } } |