120 lines
2.5 KiB
C++
120 lines
2.5 KiB
C++
/* Problem URL: https://cses.fi/problemset/task/1746 */
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#include <bits/stdc++.h>
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using namespace std;
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#define V vector
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#define rmin(a, b) a = min(a, b)
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#define rmax(a, b) a = max(a, b)
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#define rep(i, lim) for (size_t i = 0; i < (lim); i++)
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#define nrep(i, s, lim) for (size_t i = s; i < (lim); i++)
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#define repv(i, v) for (auto &i : (v))
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#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
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#define sortv(v) sort(v.begin(), v.end())
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#define all(v) (v).begin(), (v).end()
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using vi = vector<int>;
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using vvi = vector<vi>;
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using vvvi = vector<vvi>;
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using vvvvi = vector<vvvi>;
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using ll = long long;
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using vl = vector<ll>;
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using vvl = vector<vl>;
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using vvvl = vector<vvl>;
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using vvvvl = vector<vvvl>;
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template<class v>
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auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
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os << vec[0];
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for (size_t i = 1; i < vec.size(); i++) {
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os << ' ' << vec[i];
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}
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os << '\n';
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<v> &vec)->istream& {
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for (auto &i : vec) {
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is >> i;
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}
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return is;
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}
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template<class v>
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auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
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for (auto &i : vec) {
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os << i[0];
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for (size_t j = 1; j < i.size(); j++) {
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os << ' ' << i[j];
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}
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os << '\n';
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}
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
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for (auto &i : vec) {
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for (auto &j : i) {
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is >> j;
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}
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}
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return is;
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}
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const ll mod = 1e9 + 7;
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int main()
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{
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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int n, m;
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cin >> n >> m;
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vi nums(n);
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cin >> nums;
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vvl dp(n, vl(m + 1, 0));
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if (nums[0] > 0) {
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dp[0][nums[0]] = 1;
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} else {
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fill(dp[0].begin(), dp[0].end(), 1);
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dp[0][0] = 0;
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}
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nrep(i, 1, n) {
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if (nums[i] > 0) {
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ll ans = dp[i - 1][nums[i]];
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if (nums[i] < m) {
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ans += dp[i - 1][nums[i] + 1];
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}
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if (nums[i] > 1) {
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ans += dp[i - 1][nums[i] - 1];
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}
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dp[i][nums[i]] = ans % mod;
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continue;
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}
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for (size_t j = 1; j <= m; j++) {
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dp[i][j] += dp[i - 1][j];
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if (j > 1) {
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dp[i][j] += dp[i - 1][j - 1];
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}
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if (j < m) {
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dp[i][j] += dp[i - 1][j + 1];
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}
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dp[i][j] %= mod;
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}
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}
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cout << accumulate(dp[n - 1].begin(), dp[n - 1].end(), 0LL) % mod << '\n';
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}
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