Added 6 problems from Codechef's June Long Challenge One 2022

Author: leonardoAnjos16

Codechef/alternate_additions.cpp

@@ -0,0 +1,32 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        int A, B;
+        cin >> A >> B;
+
+        long mn = -1LL;
+        int l = 1, r = 1e9 + 5;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+
+            int ones = (mid + 1) / 2;
+            int twos = mid - ones;
+
+            if (A + ones + 2LL * twos < B) l = mid + 1;
+            else r = mid - 1, mn = A + ones + 2LL * twos;
+        }
+
+        bool possible = mn == B;
+        cout << (possible ? "YES" : "NO") << "\n";
+    }
+}

Codechef/divisible_by_i.cpp

@@ -0,0 +1,28 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        int N; cin >> N;
+
+        int l = 2, r = N;
+        vector<int> ans(N, 1);
+
+        for (int i = 1; i < N; i++)
+            ans[N - i - 1] = i & 1 ? r-- : l++;
+
+        for (int i = 0; i < N; i++) {
+            if (i) cout << " ";
+            cout << ans[i];
+        }
+
+        cout << "\n";
+    }
+}

Codechef/equal_strings.cpp

@@ -0,0 +1,29 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        int N; cin >> N;
+
+        string A; cin >> A;
+        string B; cin >> B;
+
+        int ans = 0;
+        for (char c = 'a'; c <= 'z'; c++) {
+            bool change = false;
+            for (int i = 0; i < N && !change; i++)
+                if (A[i] != c && B[i] == c) change = true;
+
+            ans += change;
+        }
+
+        cout << ans << "\n";
+    }
+}

Codechef/full_path_eraser.cpp

@@ -0,0 +1,60 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+vector<int> A, gcds;
+vector<vector<int>> tree;
+
+void get_gcds(int node = 0, int parent = -1) {
+    gcds[node] = A[node];
+    for (int child: tree[node])
+        if (child != parent) {
+            get_gcds(child, node);
+            gcds[node] = gcd(gcds[node], gcds[child]);
+        }
+}
+
+long solve(int node = 0, int parent = -1, long sum = 0LL) {
+    long curr = 0LL;
+    for (int child: tree[node])
+        if (child != parent)
+            curr += gcds[child];
+
+    long ans = sum + curr;
+    for (int child: tree[node])
+        if (child != parent)
+            ans = max(ans, solve(child, node, sum + curr - gcds[child]));
+
+    return ans;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        int N; cin >> N;
+
+        A.resize(N);
+        for (int i = 0; i < N; i++)
+            cin >> A[i];
+
+        tree.assign(N, vector<int>());
+        for (int i = 1; i < N; i++) {
+            int u, v;
+            cin >> u >> v;
+
+            tree[u - 1].push_back(v - 1);
+            tree[v - 1].push_back(u - 1);
+        }
+
+        gcds.resize(N);
+        get_gcds();
+
+        long ans = solve();
+        cout << ans << "\n";
+    }
+}

Codechef/possible_gcd.cpp

@@ -0,0 +1,27 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        int A, B;
+        cin >> A >> B;
+
+        if (A < B) swap(A, B);
+
+        int ans = 0;
+        for (int i = 1; i * i <= A - B; i++)
+            if ((A - B) % i == 0) {
+                if (i * i < A - B) ans += 2;
+                else ans++;
+            }
+
+        cout << ans << "\n";
+    }
+}

Codechef/reduce_to_zero.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define long long long int
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int T; cin >> T;
+    while (T--) {
+        long X, Y;
+        cin >> X >> Y;
+
+        if (!X && !Y) cout << "0\n";
+        else if (!X || !Y) cout << "-1\n";
+        else {
+            if (X > Y)
+                swap(X, Y);
+
+            long ans = 0LL;
+            while (Y - X > X) {
+                ans++;
+                X *= 2LL;
+
+                if (X > Y)
+                    swap(X, Y);
+            }
+
+            ans += 2LL * X - Y + (X < Y);
+            ans += 2LL * (Y - X);
+
+            cout << ans << "\n";
+        }
+    }
+}