complete 4674.rs 9912.rs 10826.rs 12140.rs 14452.rs 17021.rs 17386.rs 20929.rs

storage/zeta/rs/completed/20929.rs

@@ -0,0 +1,81 @@
+use std::io::stdin;
+
+struct InquireManager {
+    line: String,
+}
+
+impl InquireManager {
+    fn new() -> Self {
+        InquireManager {
+            line: String::new(),
+        }
+    }
+
+    fn inquire_to_a(&mut self, x: usize) -> usize {
+        println!("? A {}", x);
+        self.get()
+    }
+
+    fn inquire_to_b(&mut self, x: usize) -> usize {
+        println!("? B {}", x);
+        self.get()
+    }
+
+    fn get(&mut self) -> usize {
+        stdin().read_line(&mut self.line).unwrap();
+        let r = self.line.trim().parse::<usize>().unwrap();
+        self.line.clear();
+        r
+    }
+}
+
+fn main() {
+    let mut inq = InquireManager::new();
+    let n = inq.get();
+
+    let res = if n <= 4 {
+        let mut v = vec![];
+        for i in 1..=n {
+            v.push(inq.inquire_to_a(i));
+            v.push(inq.inquire_to_b(i));
+        }
+        v.sort();
+        v[n - 1]
+    } else {
+        let mut midpoint = 0;
+        let mut lo = 1;
+        let mut hi = n;
+        let mut a_of = 0;
+        let mut b_of = 0;
+        let mut a_hi = inq.inquire_to_a(n);
+        let mut b_hi = inq.inquire_to_b(n);
+        while lo < hi {
+            let mid = (hi + lo) / 2;
+            a_of = inq.inquire_to_a(mid);
+            b_of = inq.inquire_to_b(n - mid);
+            if a_of == b_of {
+                midpoint = a_of;
+                break;
+            } else if a_of > b_of {
+                hi = mid;
+                a_hi = a_of;
+            } else {
+                // a_of < b_of
+                lo = mid + 1;
+                b_hi = b_of;
+            }
+        }
+
+        if midpoint != 0 {
+            midpoint
+        } else {
+            if a_hi < b_hi {
+                a_hi
+            } else {
+                b_hi
+            }
+        }
+    };
+
+    println!("! {}", res);
+}