# define _CRT_SECURE_NO_WARNI NGS include algorithm include vector inclu

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145``` ```#define _CRT_SECURE_NO_WARNINGS #include #include #include #include #include using namespace std; #define forn(i, n) for (int i = 0; i < (n); ++i) typedef long long ll; //typedef complex base; struct base { double real; double imag; base() {} base(const double real, const double imag) : real(real), imag(imag) {}; base operator + (const base & r) const { return base(real + r.real, imag + r.imag); } base operator - (const base & r) const { return base(real - r.real, imag - r.imag); } base operator * (const base & r) const { return base(real * r.real - imag * r.imag, real * r.imag + imag * r.real); } }; const double pi = 2 * acos(0); const int MAXN = (int)3e6 + 10; char a[MAXN]; char b[MAXN]; const int systpow = 5; const int syst = pow(10, systpow) + 0.5; base A[MAXN]; base B[MAXN]; base ww[MAXN]; int ans[MAXN * 2]; inline void fft(base* a, const int n, const bool invert) { for (int i = 1; i < n; ++i) { int j = 0; for (int bit = 1, bitr = (n >> 1); bit < n; bit <<= 1, bitr >>= 1) if (i & bit) j |= bitr; if (i < j) swap(a[i], a[j]); } for (int i = 0; i < n; ++i) { ww[i] = base(cos(i * pi * 2 / n), sin(i * pi * 2 / n)); } for (int len = 1; len < n; len <<= 1) { for (int st = 0; st < n; st += 2 * len){ //base curw(1, 0); for (int j = 0; j < len; ++j){ base curw = ww[1LL * j * n / 2 / len]; if (invert) curw = base(curw.real, -curw.imag); base l = a[st + j]; base r = a[st + len + j] * curw; a[st + j] = l + r; a[st + len + j] = l - r; } } } if (invert) for (int i = 0; i < n; ++i) { a[i].real /= n; a[i].imag /= n; } } int main() { //ios_base::sync_with_stdio(false); //cin.tie(0); int t; scanf("%d\n", &t); for (int i = 0; i < t; ++i) { scanf("%s %s", a, b); //printf("%s %s\n", a, b); int na = strlen(a); int nb = strlen(b); reverse(a, a + na); reverse(b, b + nb); int n = 1; while (n * systpow < na || n * systpow < nb) n <<= 1; n <<= 1; //A.resize(n); B.resize(n); fill(A, A + n, base(0, 0)); fill(B, B + n, base(0, 0)); for (int i = 0, pos = 0; i < na; i += systpow, ++pos) { int cur = 0; for (int j = 0, p = 1; j < systpow && i + j < na; ++j, p *= 10) cur += (a[i + j] - '0') * p; A[pos].real = cur; } for (int i = 0, pos = 0; i < nb; i += systpow, ++pos) { int cur = 0; for (int j = 0, p = 1; j < systpow && i + j < nb; ++j, p *= 10) cur += (b[i + j] - '0') * p; B[pos].real = cur; } fft(A, n, false); fft(B, n, false); for (int i = 0; i < n; ++i){ A[i] = A[i] * B[i]; } fft(A, n, true); ll add = 0; int anssz = 0; for (int i = 0; i < n; ++i){ ll cur = (ll)(A[i].real + 0.5) + add; ans[anssz++] = cur % syst; add = cur / syst; } while (anssz > 1 && ans[anssz-1] == 0) --anssz; reverse(ans, ans + anssz); printf("%d", ans[0]); for (int i = 1; i < anssz; ++i) printf("%05d", ans[i]); printf("\n"); } //cout << n * 1LL * (n - 1) / 2 << endl; //cout << stupidSolve(s) << endl;*/ return 0; } ```