Add a lot more problems and a TODO list

Codeforces Round 1056 (Div. 2)/C. The Ancient Wizards' Capes.cpp

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+/* Problem URL: https://codeforces.com/contest/2155/problem/C */
+
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+template <class T, class comp = less<>>
+using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int t;
+    cin >> t;
+    while (t--) {
+        int n;
+        cin >> n;
+        vl fds(n);
+        cin >> fds;
+
+        if (n == 1) {
+            cout << (fds[0] == 1 ? "2\n" : "0\n");
+            continue;
+        }
+        
+        vi diffs(n - 1);
+        int maximal = 0;
+        rep(i, n - 1) {
+            diffs[i] = fds[i] - fds[i + 1];
+            rmax(maximal, abs(diffs[i]));
+        }
+
+        if (maximal >= 2) {
+            cout << "0\n";
+            continue;
+        }
+
+        auto findans = [&](int s) {
+            vi ans(n);
+            ans[0] = s;
+
+            vvi act(n, vi(2));
+            act[0][s] = 1;
+
+            nrep(i, 1, n) {
+                if (diffs[i - 1] == 0) {
+                    ans[i] = ans[i - 1] ^ 1;
+                    act[i][ans[i]] = 1;
+                    continue;
+                }
+
+                if (diffs[i - 1] < 0) {
+                    if (ans[i - 1] != 0) {
+                        return 0;
+                    }
+                    act[i][0] = 1;
+                    continue;
+                }
+
+                if (ans[i - 1] != 1) {
+                    return 0;
+                }
+
+                ans[i] = 1;
+                act[i][1] = 1;
+            }
+
+            nrep(i, 1, n) {
+                act[i][0] += act[i - 1][0];
+                act[n - i - 1][1] += act[n - i][1];
+            }
+
+            rep(i, n) {
+                if (fds[i] != act[i][0] + act[i][1]) {
+                    return 0;
+                }
+            }
+
+            return 1;
+        };
+        
+        cout << findans(0) + findans(1) << '\n';
+    }
+}