sysy-data/performance_c/sy/fft2.sy

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2024-04-14 22:20:29 +08:00
#include "sylib.h"
#define mod 998244353
int d;
int multiply(int a, int b){
if (b == 0) return 0;
if (b == 1) return a % mod;
int cur = multiply(a, b/2);
cur = (cur + cur) % mod;
if (b % 2 == 1) return (cur + a) % mod;
else return cur;
}
int power(int a, int b){
if (b == 0) return 1;
int cur = power(a, b/2);
cur = multiply(cur, cur);
if (b % 2 == 1) return multiply(cur, a);
else return cur;
}
#define maxlen 2097152
int temp[maxlen], a[maxlen], b[maxlen], c[maxlen];
int memmove(int dst[], int dst_pos, int src[], int len){
int i = 0;
while (i < len){
dst[dst_pos + i] = src[i];
i = i + 1;
}
return i;
}
int fft(int arr[], int begin_pos, int n, int w){
if (n == 1) return 1;
int i = 0;
while (i < n){
if (i % 2 == 0) temp[i / 2] = arr[i + begin_pos];
else temp[n / 2 + i / 2] = arr[i + begin_pos];
i = i + 1;
}
memmove(arr, begin_pos, temp, n);
fft(arr, begin_pos, n / 2, multiply(w, w));
fft(arr, begin_pos + n / 2, n / 2, multiply(w, w));
i = 0;
int wn = 1;
while (i < n / 2){
int x = arr[begin_pos + i];
int y = arr[begin_pos + i + n / 2];
arr[begin_pos + i] = (x + multiply(wn, y)) % mod;
arr[begin_pos + i + n / 2] = (x - multiply(wn, y) + mod) % mod;
wn = multiply(wn, w);
i = i + 1;
}
return 0;
}
int main(){
int n = getarray(a);
int m = getarray(b);
starttime();
d = 1;
while (d < n + m - 1){
d = d * 2;
}
fft(a, 0, d, power(3, (mod - 1) / d));
fft(b, 0, d, power(3, (mod - 1) / d));
int i = 0;
while (i < d){
a[i] = multiply(a[i], b[i]);
i = i + 1;
}
fft(a, 0, d, power(3, mod-1 - (mod-1)/d));
i = 0;
while (i < d){
a[i] = multiply(a[i], power(d, mod-2));
i = i + 1;
}
stoptime();
putarray(n + m - 1, a);
return 0;
}