From ffe30ac37c6332d0a0a755c0dcca3c281a551b8b Mon Sep 17 00:00:00 2001
From: koba-e964 <3303362+koba-e964@users.noreply.github.com>
Date: Fri, 1 Sep 2023 08:10:19 +0900
Subject: [PATCH] Add yukicoder/2037.rs

---
 yukicoder/2037.rs | 69 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 yukicoder/2037.rs

diff --git a/yukicoder/2037.rs b/yukicoder/2037.rs
new file mode 100644
index 00000000..bef08630
--- /dev/null
+++ b/yukicoder/2037.rs
@@ -0,0 +1,69 @@
+// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
+macro_rules! input {
+    ($($r:tt)*) => {
+        let stdin = std::io::stdin();
+        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
+        let mut next = move || -> String{
+            bytes.by_ref().map(|r|r.unwrap() as char)
+                .skip_while(|c|c.is_whitespace())
+                .take_while(|c|!c.is_whitespace())
+                .collect()
+        };
+        input_inner!{next, $($r)*}
+    };
+}
+
+macro_rules! input_inner {
+    ($next:expr) => {};
+    ($next:expr,) => {};
+    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
+        let $var = read_value!($next, $t);
+        input_inner!{$next $($r)*}
+    };
+}
+
+macro_rules! read_value {
+    ($next:expr, chars) => {
+        read_value!($next, String).chars().collect::<Vec<char>>()
+    };
+    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
+}
+
+fn one_step(s: Vec<char>) -> Vec<char> {
+    let n = s.len();
+    let mut ans = vec!['1'; n - 1];
+    for i in 0..n - 1 {
+        if s[i] == '1' && s[i + 1] == '1' {
+            ans[i] = '0';
+        }
+    }
+    ans
+}
+
+// https://yukicoder.me/problems/no/2037 (3)
+// 2 段上に上ると、元々の列のうち、
+// (i) 1 が 1 個だけあるところは 0 になる
+// (ii) それ以外は同じ数字のまま
+// が成り立つ。これを利用して実装できる。
+fn main() {
+    input! {
+        n: usize, k: usize,
+        s: chars,
+    }
+    let med = if (k + n) % 2 == 1 { n - 1 } else { n };
+    let mut s = s;
+    if med < n {
+        s = one_step(s);
+    }
+    assert_eq!((k + med) % 2, 0);
+    if k < med {
+        for i in 1..s.len() - 1 {
+            if s[i - 1..i + 2] == ['0', '1', '0'] {
+                s[i] = '0';
+            }
+        }
+    }
+    let x = (med - k) / 2;
+    let ans: String = s[x..s.len() - x].iter().cloned().collect();
+    println!("{}", ans);
+}