Yukicoder No.619 CardShuffle
solution
類問としてJAG Practice Contest for ACM-ICPC Asia Regional 2016: J - Compressed Formulaがある (解説)。 これと同様に各文字を行列に写しsegment木で管理すればよい。$O(Q \log N)$。
implementation
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; (i) < int(n); ++ (i))
#define REP_R(i, n) for (int i = int(n) - 1; (i) >= 0; -- (i))
using ll = long long;
using namespace std;
template <class Monoid>
struct segment_tree {
typedef typename Monoid::underlying_type underlying_type;
int n;
vector<underlying_type> a;
Monoid mon;
segment_tree() = default;
segment_tree(int a_n, underlying_type initial_value = Monoid().unit(), Monoid const & a_mon = Monoid()) : mon(a_mon) {
n = 1; while (n < a_n) n *= 2;
a.resize(2 * n - 1, mon.unit());
fill(a.begin() + (n - 1), a.begin() + ((n - 1) + a_n), initial_value); // set initial values
REP_R (i, n - 1) a[i] = mon.append(a[2 * i + 1], a[2 * i + 2]); // propagate initial values
}
void point_set(int i, underlying_type z) { // 0-based
a[i + n - 1] = z;
for (i = (i + n) / 2; i > 0; i /= 2) { // 1-based
a[i - 1] = mon.append(a[2 * i - 1], a[2 * i]);
}
}
underlying_type range_concat(int l, int r) { // 0-based, [l, r)
underlying_type lacc = mon.unit(), racc = mon.unit();
for (l += n, r += n; l < r; l /= 2, r /= 2) { // 1-based loop, 2x faster than recursion
if (l % 2 == 1) lacc = mon.append(lacc, a[(l ++) - 1]);
if (r % 2 == 1) racc = mon.append(a[(-- r) - 1], racc);
}
return mon.append(lacc, racc);
}
};
constexpr int mod = 1e9 + 7;
constexpr int N = 4;
typedef array<ll, N> vec4;
typedef array<array<ll, N>, N> mat44;
mat44 operator * (mat44 const & a, mat44 const & b) {
mat44 c = {};
REP (k, N) REP (i, N) REP (j, N) (c[i][j] += a[i][k] * b[k][j]) %= mod;
return c;
}
vec4 operator * (mat44 const & a, vec4 const & b) {
vec4 c = {};
REP (k, N) REP (i, N) (c[i] += a[i][k] * b[k]) %= mod;
return c;
}
mat44 to_matrix(ll (& a)[N][N]) {
mat44 b = {};
REP (i, N) REP (j, N) b[i][j] = a[i][j];
return b;
}
mat44 unit_matrix() {
mat44 f = {};
REP (i, N) f[i][i] = 1;
return f;
}
struct matmul_monoid {
typedef mat44 underlying_type;
underlying_type unit() const { return unit_matrix(); }
underlying_type append(underlying_type const & a, underlying_type const & b) const { return b * a; }
};
mat44 digit(int d) {
ll f[N][N] = {
{ 1, 0, 0, 0 },
{ 0, 1, 0, 0 },
{ 0, d, 10, 0 },
{ 0, 0, 0, 1 },
};
return to_matrix(f);
}
mat44 mult() {
ll f[N][N] = {
{ 1, 0, 0, 0 },
{ 0, 0, 1, 0 },
{ 0, 0, 0, 0 },
{ 0, 0, 0, 1 },
};
return to_matrix(f);
}
mat44 add(bool is_positive = true) {
ll f[N][N] = {
{ 1, 0, 1, 0 },
{ 0, 0, 0, is_positive ? 1 : -1 },
{ 0, 0, 0, 0 },
{ 0, 0, 0, 1 },
};
return to_matrix(f);
}
int get_result(mat44 const & f) {
vec4 x { { 0, 1, 0, 1 } };
vec4 y = f * x;
return (y[0] + y[2]) % mod;
}
int main() {
// prepare
int n; scanf("%d", &n);
vector<char> c(n); REP (i, n) scanf(" %c", &c[i]);
segment_tree<matmul_monoid> segtree(n);
auto update = [&](int i) {
mat44 a =
c[i] == '+' ? add() :
c[i] == '*' ? mult() :
digit(c[i] - '0');
segtree.point_set(i, a);
};
REP (i, n) update(i);
// serve
int q; scanf("%d", &q);
while (q --) {
char t; int x, y; scanf(" %c%d%d", &t, &x, &y); -- x; -- y;
if (t == '!') {
swap(c[x], c[y]);
update(x);
update(y);
} else if (t == '?') {
int result = get_result(segtree.range_concat(x, y + 1));
printf("%d\n", result);
}
}
return 0;
}