From 3ea364020925aabaf465f4d4baab03f076047735 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Fri, 2 Dec 2022 16:40:22 +0800
Subject: [PATCH] =?UTF-8?q?P3803=20=E3=80=90=E6=A8=A1=E6=9D=BF=E3=80=91?=
 =?UTF-8?q?=E5=A4=9A=E9=A1=B9=E5=BC=8F=E4=B9=98=E6=B3=95=EF=BC=88FFT?=
 =?UTF-8?q?=EF=BC=89?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

https://www.luogu.com.cn/record/96299698
---
 Luogu/P3803/P3803.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Luogu/P3803/P3803.cpp b/Luogu/P3803/P3803.cpp
index 20c88a28..487f5dec 100644
--- a/Luogu/P3803/P3803.cpp
+++ b/Luogu/P3803/P3803.cpp
@@ -22,7 +22,9 @@ constexpr long long binpow(long long a, long long b) {
     return res;
 }
 
-std::vector<long long> number_theoretic_transform(std::vector<long long> a) {
+void number_theoretic_transform(std::vector<long long> &a) {
+    if (a.size() == 1) return;
+
     // assert(a.size() == (1 << std::__lg(a.size())));
     int k = std::__lg(a.size());
 
@@ -55,8 +57,6 @@ std::vector<long long> number_theoretic_transform(std::vector<long long> a) {
             }
         }
     }
-
-    return a;
 }
 
 class Poly : public std::vector<long long> {
@@ -81,15 +81,15 @@ class Poly : public std::vector<long long> {
         std::vector<long long> f(*this), g(b);
 
         f.resize(k);
-        f = number_theoretic_transform(f);
+        number_theoretic_transform(f);
         g.resize(k);
-        g = number_theoretic_transform(g);
+        number_theoretic_transform(g);
 
         for (int i = 0; i < k; i++) {
             f[i] = f[i] * g[i] % mod;
         }
 
-        f = number_theoretic_transform(f);
+        number_theoretic_transform(f);
         // assert(f.size() > 0)
         std::reverse(f.begin() + 1, f.end());