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Author: BrandonTang89

Other_Tasks/CF2066_A_Object_Identification.py

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+import sys
+for _ in range(int(input())):
+
+    n = int(input())   
+    xs = [int(x) for x in input().split()]
+    
+    # MEX
+    mex = 1
+    s = set(xs)
+    while mex in s:
+        mex += 1
+    
+    if mex < n+1:
+        print(f"? {mex} {1 if mex > 1 else 2}")
+        sys.stdout.flush()
+        res = int(input())
+        if res == 0:
+            print(f"! A")
+            sys.stdout.flush()
+        else:
+            print(f"! B")
+            sys.stdout.flush()
+    else:
+        for i in range(n):
+            if xs[i] == 1:
+                a = i+1
+            if xs[i] == n:
+                b = i+1
+                
+        assert a is not None and b is not None
+        
+        print(f"? {a} {b}")
+        sys.stdout.flush()
+        
+        res = int(input())
+        if res < n-1: 
+            print(f"! A")
+            sys.stdout.flush()
+        else:
+            print(f"? {b} {a}")
+            sys.stdout.flush()
+            res = int(input())
+            if res < n-1:
+                print(f"! A")
+                sys.stdout.flush()
+            else:
+                print(f"! B")
+                sys.stdout.flush()

Other_Tasks/CF2066_B_White_Magic.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;
+
+int n;
+multiset<int> s;
+int main(){
+    int tc;
+    cin >> tc;
+    while(tc--){
+        cin >> n;
+        vector<int> arr(n);
+        s.clear();
+        int numZeros = 0;
+        int firstZero = -1;
+        for(int i = 0; i < n; i++){
+            cin >> arr[i];
+            s.insert(arr[i]);
+
+            if (arr[i] == 0){
+                numZeros++;
+                if (firstZero == -1){
+                    firstZero = i;
+                }
+                else{
+                    s.erase(s.find(0));
+                }
+            }
+        }
+        if (numZeros == 0){
+            cout << n << endl;
+            continue;
+        }
+
+        int mex = 0;
+        while(s.find(mex) != s.end()){
+            mex++;
+        }
+        
+        // We try the whole sequence with the first zero (exclude all the other zeros)
+        bool can = true;
+        int mini = INT_MAX;
+        for (int i=0; i<n; i++){
+            if (arr[i] == 0){
+                break;
+            }
+            
+            mini = min(mini, arr[i]);
+            s.erase(s.find(arr[i]));
+            if (arr[i] < mex && s.find(arr[i]) == s.end()){
+                mex = arr[i];
+            }
+
+            if (mini < mex){
+                can = false;
+                break;
+            }
+        }
+
+        if (can){
+            cout << n - numZeros + 1<< endl;
+        }
+        else{
+            cout << n - numZeros << endl;
+        }
+    }
+
+    return 0;
+}

Other_Tasks/CF2066_C_Bitwise_Slides.cpp

@@ -0,0 +1,71 @@
+#pragma GCC optimize("Ofast")
+#pragma GCC optimize("unroll-loops")
+#include <bits/stdc++.h>  
+using namespace std;
+
+typedef long long ll;
+
+int n;
+vector<int> jmp; // jmp[i] = j means a[i] XOR ... XOR a[j] = 0 and j is the smallest possible
+vector<int> a;
+
+ll MOD = 1e9 + 7;
+vector<vector<ll>> memo;
+
+ll dp(int idx, int t){
+    // t = 0 => number of ways to finish given that the next index to choose is idx and v[X] = a[idx-1] for exactly one X in {0, 1, 2}
+    // t = 1 => number of ways to finish given that the next index to choose is idx and v[0] = v[1] = v[2] = 0
+
+    if (idx == n) return 1;
+    if (memo[idx][t] != -1) return memo[idx][t];
+
+    ll ans = 0;
+    if (t == 1){
+        if (jmp[idx] == -1){
+            ans = 3;
+        }
+        else{
+            ans = (dp(jmp[idx]+1, 1) * 3) % MOD;
+            ans += (dp(jmp[idx]+1, 0) * 6) % MOD;
+        }
+    }
+    else{
+        if (jmp[idx-1] == -1){
+            ans = 1;
+        }
+        else{
+            ans = (dp(jmp[idx-1]+1, 1) * 1) % MOD;
+            ans += (dp(jmp[idx-1]+1, 0) * 2) % MOD;
+        }
+    }
+
+    return memo[idx][t] = ans % MOD;
+}
+
+int main(){
+    int tc;
+    cin >> tc;
+    while(tc--){
+        cin >> n;
+        a.resize(n);
+        jmp.assign(n, -1);
+
+        vector<int> prefixXor(n);
+        map<int, int> m; // m[x] = i means a[0] XOR ... XOR a[i] = x 
+        m[0] = -1;
+        for(int i = 0; i < n; i++){
+            cin >> a[i];
+            prefixXor[i] = a[i] ^ (i == 0 ? 0 : prefixXor[i-1]);
+
+            if (m.find(prefixXor[i]) != m.end()){
+                jmp[m[prefixXor[i]] + 1] = i;
+            }
+            m[prefixXor[i]] = i;
+        }
+        
+        memo.assign(n, vector<ll>(2, -1));
+        cout << dp(0, 1) << endl;
+    }
+
+    return 0;
+}