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Author: BrandonTang89

Other_Tasks/CF2071_A_The_Play_Never_Ends.py

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+for _ in range(int(input())):
+    print("YES" if (int(input()) - 1) % 3 == 0 else "NO")

Other_Tasks/CF2071_B_Perfecto.py

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+
+from functools import lru_cache
+
+@lru_cache(maxsize=None)
+def isSquare(n):
+    if n == 0 or n == 1:
+        return True
+
+    start = 1
+    end = n
+    while start <= end:
+        mid = (start + end) // 2
+        if mid * mid == n:
+            return True
+        elif mid * mid < n:
+            start = mid + 1
+        else:
+            end = mid - 1
+    return False
+
+
+for _ in range(int(input())):
+    n = int(input())
+    
+    s = 0
+    i = 1
+    ans = []
+    while i < n+1:
+        s += i
+        if isSquare(s):
+            if i == n:
+                ans = [-1]
+                break
+            else:
+                ans.append(i+1)
+                ans.append(i)
+                s += i+1
+                i += 2
+        else:
+            ans.append(i)
+            i += 1
+    
+    print(" ".join(map(str, ans)))

Other_Tasks/CF2071_C_Trapmigiano_Reggiano.cpp

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+#pragma GCC optimize("Ofast")
+#pragma GCC optimize("unroll-loops")
+#include <bits/stdc++.h>  
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+#define fast_cin() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
+
+
+int main(){
+    int tc;
+    cin >> tc;
+    while (tc--){
+        int n, st, en;
+        cin >> n >> st >> en;
+        st--, en--;
+        vector<vector<int>> adjlist(n, vector<int>());
+        for (int i=0; i<n-1; i++){
+            int u, v;
+            cin >> u >> v;
+            u--, v--;
+            adjlist[u].push_back(v);
+            adjlist[v].push_back(u);
+        }
+        
+        // we first find the shortest path from S to E
+        vector<int> dist(n, -1);
+        queue<int> q;
+        q.push(st);
+        dist[st] = 0;
+        while (!q.empty()){
+            int u = q.front();
+            q.pop();
+            for (int v : adjlist[u]){
+                if (dist[v] == -1){
+                    dist[v] = dist[u] + 1;
+                    q.push(v);
+                }
+            }
+        }
+        vector<int> path;
+        path.push_back(en);
+        int cur = en;
+        while (cur != st){
+            for (int v : adjlist[cur]){
+                if (dist[v] == dist[cur] - 1){
+                    path.push_back(v);
+                    cur = v;
+                    break;
+                }
+            }
+        }
+        reverse(path.begin(), path.end());
+        unordered_set<int> path_set(path.begin(), path.end());
+        
+
+        // now we traverse along the path, exploring the surrounding sub trees first before going down the path
+        vector<int> ans;
+        dist.assign(n, -1);
+        vector<pair<int, int>> subtree; // dist, node
+        int pathLen = path.size();
+        for (int i=0; i<pathLen; i++){
+            int root = path[i];
+            dist[root] = 0;
+            for (int v : adjlist[root]){
+                if (path_set.find(v) == path_set.end()){
+                    q.push(v);
+                    dist[v] = 1;
+                }
+            }
+
+            while (!q.empty()){
+                int u = q.front();
+                subtree.push_back({dist[u], u});
+                q.pop();
+                for (int v : adjlist[u]){
+                    if (dist[v] == -1){
+                        dist[v] = dist[u] + 1;
+                        q.push(v);
+
+                    }
+                }
+            }
+
+            for (auto it = subtree.rbegin(); it != subtree.rend(); it++){
+                ans.push_back(it->second + 1);
+            }
+
+            subtree.clear();
+            ans.push_back(root + 1);
+        }
+
+        for (auto x: ans){
+            cout << x << " ";
+        }
+        cout << endl;
+
+    }
+
+
+
+    return 0;
+}

Other_Tasks/CF2071_D_1_Infinite_Sequence_Easy_Version.cpp

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+#pragma GCC optimize("Ofast")
+#pragma GCC optimize("unroll-loops")
+#include <bits/stdc++.h>  
+using namespace std;
+
+typedef long long ll;
+typedef vector<int> vi;
+#define fast_cin() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
+
+template <typename T=int>
+struct StaticSum {
+    const int n;
+    vector<T> pfs;  // arr[i] contains the range sum from 0 to i inclusively
+
+    T rsq(int l, int r) const {            // range sum from l to r inclusively
+        if (l < 0 || r >= n) assert(false);  // boundary condition check
+        if (l == 0) return pfs[r];
+        return (pfs[r] ^ pfs[l - 1]);
+    }
+
+    StaticSum(const vector<T>& arr) : n(arr.size()), pfs(arr) {
+        for (int i = 1; i < n; i++) {
+            pfs[i] ^= pfs[i - 1];
+        }
+    }
+};
+
+
+int main(){
+    int tc;
+    cin >> tc;
+    while (tc--){
+        int n;
+        ll q;
+        cin >> n >> q >> q;
+        vector<int> v(n+1);
+        for (int i=0; i<n; i++){
+            cin >> v[i+1];
+        }
+        
+
+        if (n%2 == 0){ // make n odd
+            int acc = 0;
+            for (int i=1;i<=n/2; i++){
+                acc ^= v[i];
+            }
+            v.emplace_back(acc);
+            n++;
+        }
+
+        StaticSum<int> ss(v);
+        
+        int ans = 0;
+        while (q > 0){
+            if (q <= n){
+                cout << (v[q] ^ ans) << endl;
+                break;
+            }
+            else if (q / 2LL <= n){
+                cout << (ss.rsq(1, q/2LL) ^ ans) << endl;
+                break;
+            }
+            else if ((q / 2LL) %2 == 1){
+                cout << (ss.rsq(1, n) ^ ans) << endl;
+                break;
+            } 
+            else{
+                q = (q/2LL);
+                ans ^= ss.rsq(1, n);
+            }
+        }
+
+
+    }
+
+
+    return 0;
+}