1 files changed, 108 insertions, 0 deletions
diff --git a/2020/January/nondec.cpp b/2020/January/nondec.cpp
new file mode 100644
index 0000000..2084a05
--- /dev/null
+++ b/2020/January/nondec.cpp
@@ -0,0 +1,108 @@
+#include <bits/stdc++.h>
+#include <ext/pb_ds/tree_policy.hpp>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/rope>
+#define FOR(i, a, b, in) for (int i = (a); i < (b); i += in)
+#define REP(i, a, b) for (int i = (a); i < (b); i++)
+#define RFOR(i, a, b, in) for (int i = (a) - 1; i >= (b); i -= in)
+#define RREP(i, a, b) for (int i = (a) - 1; i >= (b); i--)
+#define trav(a, x) for (auto& a : x)
+#define mp make_pair
+#define pb push_back
+#define eb emplace_back
+#define f first
+#define s second
+#define lb lower_bound
+#define ub upper_bound
+#define sz(x) (int)x.size()
+#define all(x) begin(x), end(x)
+#define rsz resize
+#define mem(a, b) memset(a, (b), sizeof(a))
+using namespace std;
+using namespace __gnu_pbds;
+using namespace __gnu_cxx;
+typedef string str;
+typedef long long ll;
+typedef long double ld;
+typedef complex<ld> cd;
+typedef pair<int, int> ii; typedef pair<ll, ll> pl; typedef pair<ld, ld> pd;
+typedef vector<int> vi; typedef vector<ll> vl; typedef vector<ld> vd;
+typedef vector<ii> vii; typedef vector<pl> vpl; typedef vector<pd> vpd;
+typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
+typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_multiset; // WARNING: May be broken
+constexpr int INF = 1e9;
+constexpr ll LINF = 1e18;
+const ll MOD = 1e9+7;
+const ll INV = 5e8+4;
+const int S = 200;
+const ld PI = 4*atan((ld)1);
+void io(str s) {
+    if (fopen((s+".in").c_str(), "r")) {
+        freopen((s+".in").c_str(), "r", stdin);
+        freopen((s+".out").c_str(), "w", stdout);
+    } 
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL), cout.tie(NULL);
+}
+
+
+int N, K, A[50001], cl[50001][21], cr[50001][21], ans[200001];
+
+void solve(int l, int r, vector<pair<ii, int>>& q) {
+    int m = (l + r) >> 1;
+    for (int i = l; i <= r; i++) memset(cl[i], 0, sizeof(cl[i])), memset(cr[i], 0, sizeof(cr[i]));
+    int c[21][21] = { 0 };
+    for (int i = m; i >= l; i--) {
+        if (i < m) memcpy(cl[i], cl[i + 1], sizeof(cl[i]));
+        for (int j = A[i]; j <= K; j++) {
+            for (int k = A[i]; k <= K; k++) {
+                cl[i][j] = (c[k][j] + cl[i][j]) % MOD;
+                c[A[i]][j] = (c[k][j] + c[A[i]][j]) % MOD;
+            }
+        }
+        cl[i][A[i]]++, c[A[i]][A[i]]++;
+    }
+    memset(c, 0, sizeof(c));
+    for (int i = m + 1; i <= r; i++) {
+        if (i > m + 1) memcpy(cr[i], cr[i - 1], sizeof(cr[i]));
+        for (int j = A[i]; j > 0; j--) {
+            for (int k = A[i]; k > 0; k--) {
+                cr[i][j] = (c[j][k] + cr[i][j]) % MOD;
+                c[j][A[i]] = (c[j][k] + c[j][A[i]]) % MOD;
+            }
+        }
+        cr[i][A[i]]++, c[A[i]][A[i]]++;
+    }
+    vector<pair<ii, int>> ql, qr;
+    for (auto& x : q) {
+        if (x.f.f <= m && x.f.s > m) {
+            ll cnt = 0;
+            for (int i = 1; i <= K; i++) {
+                cnt = (cl[x.f.f][i] + cnt) % MOD;
+                ans[x.s] = (cnt * cr[x.f.s][i] + cl[x.f.f][i] + cr[x.f.s][i] + ans[x.s]) % MOD;
+            }
+        }
+        else if (x.f.s <= m) ql.pb(x);
+        else qr.pb(x);
+    }
+    if (l == r) return;
+    solve(l, m, ql), solve(m + 1, r, qr);
+}
+
+int main() {
+    io("nondec");
+
+    cin >> N >> K;
+    for (int i = 0; i < N; i++) cin >> A[i];
+
+    int Q;
+    cin >> Q;
+    vector<pair<ii, int>> q(Q);
+    for (int i = 0; i < Q; i++) {
+        cin >> q[i].f.f >> q[i].f.s;
+        q[i].f.f--, q[i].f.s--;
+        q[i].s = i;
+    }
+    solve(0, N - 1, q);
+    for (int i = 0; i < Q; i++) cout << ans[i] + (q[i].f.f == q[i].f.s) + 1 << '\n';    
+}