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March 8, 2022 13:50
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Boj 22289
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#include <iostream> | |
#include <algorithm> | |
#include <vector> | |
#include <complex> | |
#include <cstring> | |
using namespace std; | |
typedef complex<double> cpx; | |
#define C(X) (cpx(X)) | |
const double PI = acos(-1); | |
void DFT(vector<cpx>& f, cpx w) { | |
auto n = f.size(); | |
if(n == 1) return; | |
vector<cpx> odd(n / 2), even(n / 2); | |
for(int i = 0; i < n; i++) | |
(i % 2 ? odd : even)[i / 2] = f[i]; | |
DFT(odd, w * w); | |
DFT(even, w * w); | |
cpx wp = cpx(1, 0); | |
for(int i = 0; i < n / 2; i++) { | |
f[i] = even[i] + wp * odd[i]; | |
f[i + n / 2] = even[i] - wp * odd[i]; | |
wp *= w; | |
} | |
} | |
void IDFT(vector<cpx>& f, cpx w) { | |
DFT(f, cpx(1, 0) / w); | |
} | |
vector<int> mul(vector<cpx>& a, vector<cpx>& b) { | |
auto a_size = a.size(); | |
auto b_size = b.size(); | |
int n = 1; | |
while(n <= a_size || n <= b_size) n <<= 1; | |
n <<= 1; | |
a.resize(n); | |
b.resize(n); | |
vector<cpx> c(n); | |
cpx w(cos(2 * PI / n), sin(2 * PI / n)); | |
DFT(a, w); | |
DFT(b, w); | |
for(int i = 0; i < n; i++) | |
c[i] = a[i] * b[i]; | |
IDFT(c, w); | |
vector<int> o(n); | |
for(int i = 0; i < n; i++) { | |
o[i] = round(c[i].real() / n); | |
} | |
return o; | |
} | |
int main() { | |
char* a = (char*)malloc(1000005); | |
char* b = (char*)malloc(1000005); | |
scanf("%s %s", a, b); | |
if(*a == '0' || *b == '0') { | |
printf("0"); | |
return 0; | |
} | |
int len_a = strlen(a); | |
int a_siz = (len_a + 1) / 2; | |
auto v1 = vector<cpx>(a_siz); | |
if(len_a % 2) { | |
v1[0] = *a - '0'; | |
for (int i = 1; i < a_siz; i++) | |
v1[i] = C(10 * (a[i * 2 - 1] - '0') + a[i * 2] - '0'); | |
} | |
else for (int i = 0; i < a_siz; i++) | |
v1[i] = C(10 * (a[i * 2] - '0') + a[i * 2 + 1] - '0'); | |
int len_b = strlen(b); | |
int b_siz = (len_b + 1) / 2; | |
auto v2 = vector<cpx>(b_siz); | |
if(len_b % 2) { | |
v2[0] = *b - '0'; | |
for (int i = 1; i < b_siz; i++) | |
v2[i] = C(10 * (b[i * 2 - 1] - '0') + b[i * 2] - '0'); | |
} | |
else for (int i = 0; i < b_siz; i++) | |
v2[i] = C(10 * (b[i * 2] - '0') + b[i * 2 + 1] - '0'); | |
auto v3 = mul(v1, v2); | |
int t = 0; | |
for(int i = a_siz + b_siz - 2; i >= 0; i--) { | |
v3[i] += t; | |
if(v3[i] >= 100) { | |
t = v3[i] / 100; | |
v3[i] %= 100; | |
} | |
else t = 0; | |
} | |
if(t) { | |
printf("%d", t); | |
if(v3[0] < 10) | |
printf("0%d", v3[0]); | |
else printf("%d", v3[0]); | |
} | |
else printf("%d", v3[0]); | |
for(int i = 1; i < a_siz + b_siz - 1; i++) | |
if(v3[i] < 10) | |
printf("0%d", v3[i]); | |
else printf("%d", v3[i]); | |
return 0; | |
} |
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https://www.acmicpc.net/problem/22289