Add yukicoder/2846.rs yukicoder/2847.rs

yukicoder/2846.rs

@@ -0,0 +1,55 @@
+use std::io::Read;
+
+fn get_word() -> String {
+    let stdin = std::io::stdin();
+    let mut stdin=stdin.lock();
+    let mut u8b: [u8; 1] = [0];
+    loop {
+        let mut buf: Vec<u8> = Vec::with_capacity(16);
+        loop {
+            let res = stdin.read(&mut u8b);
+            if res.unwrap_or(0) == 0 || u8b[0] <= b' ' {
+                break;
+            } else {
+                buf.push(u8b[0]);
+            }
+        }
+        if buf.len() >= 1 {
+            let ret = String::from_utf8(buf).unwrap();
+            return ret;
+        }
+    }
+}
+
+fn get<T: std::str::FromStr>() -> T { get_word().parse().ok().unwrap() }
+
+// https://yukicoder.me/problems/no/2846 (3)
+// irb(main):009> [24,22,21,20,18,16,15,14,13,12,11,10,9,8,7,6,5].reduce{|a,b|a.lcm(b)}
+// => 720720
+// 素数 23, 19, 17 だけ特別扱いして、あとは幅 720720 の DP で解く。
+fn main() {
+    let k: usize = get();
+    let n: usize = get();
+    const W: usize = 720_720;
+    let prs = [23, 19, 17];
+    let mut dp = vec![0i64; W + 1];
+    dp[0] = 1;
+    for _ in 0..k {
+        let mut ep = vec![0; W + 1];
+        for i in 1..n + 1 {
+            if W % i != 0 { continue; }
+            let x = W / i;
+            for j in x..W + 1 {
+                ep[j] += dp[j - x];
+            }
+        }
+        dp = ep;
+    }
+    let mut ans = dp[W];
+    for &p in &prs {
+        if k == p {
+            ans += 1;
+        }
+    }
+    println!("{}", ans);
+}

yukicoder/2847.rs

@@ -0,0 +1,77 @@
+use std::io::Read;
+
+fn get_word() -> String {
+    let stdin = std::io::stdin();
+    let mut stdin=stdin.lock();
+    let mut u8b: [u8; 1] = [0];
+    loop {
+        let mut buf: Vec<u8> = Vec::with_capacity(16);
+        loop {
+            let res = stdin.read(&mut u8b);
+            if res.unwrap_or(0) == 0 || u8b[0] <= b' ' {
+                break;
+            } else {
+                buf.push(u8b[0]);
+            }
+        }
+        if buf.len() >= 1 {
+            let ret = String::from_utf8(buf).unwrap();
+            return ret;
+        }
+    }
+}
+
+fn get<T: std::str::FromStr>() -> T { get_word().parse().ok().unwrap() }
+
+fn gcd(a: i64, b: i64) -> i64 {
+    if b == 0 {
+        a
+    } else {
+        gcd(b, a % b)
+    }
+}
+
+fn calc(x: i64, y: i64, a: i64, b: i64) -> i64 {
+    (x - a).max(0) * (y - b).max(0)
+}
+
+// https://yukicoder.me/problems/no/2847 (3.5)
+// a^2 + b^2 が平方数となる (a, b) 全てに対して、(2 * a, 2 * b) だけ離れた点を数える必要がある。
+// a^2 + b^2 が平方数となる (a, b) の列挙は、1+i や有理整数で割り切れないガウス整数を列挙することで行える。
+// Tags: enumerating-gaussian-integers-with-square-norm
+fn main() {
+    let x: i64 = get();
+    let y: i64 = get();
+    let m: i64 = get();
+    let mut tot = 0;
+    for a in 1..=x / 2 {
+        tot += calc(x, y, 2 * a, 0);
+        tot %= m;
+    }
+    for a in 1..=y / 2 {
+        tot += calc(x, y, 0, 2 * a);
+        tot %= m;
+    }
+    for a in 1..2001 {
+        for b in 1..2001 {
+            if (a + b) % 2 == 0 {
+                continue;
+            }
+            if gcd(a, b) != 1 {
+                continue;
+            }
+            let c = a * a - b * b;
+            let d = 2 * a * b;
+            let (c, d) = if c < 0 {
+                (d, -c)
+            } else {
+                (c, d)
+            };
+            for s in 1..=(x / 2 / c).min(y / 2 / d) {
+                tot += calc(x, y, c * 2 * s, d * 2 * s) * 2;
+                tot %= m;
+            }
+        }
+    }
+    println!("{}", tot * 2 % m);
+}