sudoku: 1654 A

Author: Rubix982

.vscode/settings.json

@@ -44,6 +44,12 @@
     "typeinfo": "cpp",
     "variant": "cpp",
     "algorithm": "cpp",
-    "tuple": "cpp"
+    "tuple": "cpp",
+    "barrier": "cpp",
+    "latch": "cpp",
+    "semaphore": "cpp",
+    "valarray": "cpp",
+    "chrono": "cpp",
+    "random": "cpp"
   }
 }

projects/sudoku/src/1654_A.cpp

@@ -0,0 +1,53 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define fastio()                 \
+    ios::sync_with_stdio(false); \
+    cin.tie(nullptr);
+// g++-15 -std=c++17 -O2 -Wall 897_A.cpp -o 897_A
+
+using ll = long long;
+
+void solve()
+{
+    int n;
+    cin >> n;
+    vector<ll> a(n);
+    for (int i = 0; i < n; i++)
+        cin >> a[i];
+
+    // original maximum adjacent sum
+    ll orig = 0;
+    for (int i = 0; i + 1 < n; ++i)
+        orig = max(orig, a[i] + a[i + 1]);
+
+    // prefix max and suffix max arrays
+    vector<ll> pref(n), suf(n);
+    pref[0] = a[0];
+    for (int i = 1; i < n; ++i)
+        pref[i] = max(pref[i - 1], a[i]);
+    suf[n - 1] = a[n - 1];
+    for (int i = n - 2; i >= 0; --i)
+        suf[i] = max(suf[i + 1], a[i]);
+
+    // max over a[r] + max_{0..r-1} a[p]
+    ll best1 = 0;
+    for (int r = 1; r < n; ++r)
+        best1 = max(best1, a[r] + pref[r - 1]);
+
+    // max over a[l] + max_{l+1..n-1} a[q]
+    ll best2 = 0;
+    for (int l = 0; l + 1 < n; ++l)
+        best2 = max(best2, a[l] + suf[l + 1]);
+
+    cout << max({orig, best1, best2}) << '\n';
+}
+
+int main()
+{
+    fastio();
+    int T = 1;
+    cin >> T;
+    while (T--)
+        solve();
+    return 0;
+}

projects/sudoku/src/1654_A.txt

@@ -0,0 +1,11 @@
+5
+6
+5 2 1 4 7 3
+3
+32 78 78
+3
+69 54 91
+8
+999021 999021 999021 999021 999652 999021 999021 999021
+2
+1000000000 1000000000