Consider the following grammar:
- <expression> ::= <term> | <expression> ‘+’ <term>
- <term> ::= <number> | <number> ‘-‘ <number> | <number> ‘(‘ <expression> ‘)’
- <number> ::= <pos_digit> | <number> <digit>
- <digit> ::= ‘0’ | <pos_digit>
- <pos_digit> ::= ‘1’ | ‘2’ | ‘3’ | ‘4’ | ‘5’ | ‘6’ | ‘7’ | ‘8’ | ‘9’
This grammar describes a number in decimal system using the following rules:
- <number> describes itself,
- <number>-<number> (l-r, l ≤ r) describes integer which is concatenation of all integers from l to r, written without leading zeros. For example, 8-11 describes 891011,
- <number>(<expression>) describes integer which is concatenation of <number> copies of integer described by <expression>,
- <expression>+<term> describes integer which is concatenation of integers described by <expression> and <term>.
For example, 2(2-4+1)+2(2(17)) describes the integer 2341234117171717.
You are given an expression in the given grammar. Print the integer described by it modulo 109 + 7.
Input
The only line contains a non-empty string at most 105 characters long which is valid according to the given grammar. In particular, it means that in terms l-r l ≤ r holds.
Output
Print single integer — the number described by the expression modulo 109 + 7.
Examples
input
8-11
output
891011
input
2(2-4+1)+2(2(17))
output
100783079
input
1234-5678
output
745428774
input
1+2+3+4-5+6+7-9
output
123456789
Solution:
#include <bits/stdc++.h> using namespace std; const int MOD = 1000000007; inline void add(int &a, int b, int md = MOD) { a += b; if (a >= md) { a -= md; } } inline int mul(int a, int b, int md = MOD) { return (long long) a * b % md; } inline int power(int a, int b, int md = MOD) { int res = 1; while (b > 0) { if (b & 1) { res = mul(res, a, md); } a = mul(a, a, md); b >>= 1; } return res; } inline int inv(int x) { return power(x, MOD - 2); } struct node { int value; int len; }; node seq(int n7, int n6, int k) { int p10k = power(10, k); int t = mul(p10k, 10); int e = n6 - power(10, k, MOD - 1) + 1; if (e < 0) { e += MOD - 1; } int it1 = inv(t - 1); int sum = mul(power(t, e) + MOD - 1, it1); int z = mul(p10k, sum); int res = z; int cnt = n7 - p10k + 1; if (cnt < 0) { cnt += MOD; } add(res, mul(sum - cnt + MOD, it1)); return {res, mul(e, k + 1, MOD - 1)}; } node concat(node a, node b) { int value = mul(a.value, power(10, b.len)); add(value, b.value); return {value, (a.len + b.len) % (MOD - 1)}; } node multi(node a, int b) { if (b == 1) { return a; } if (b % 2 == 1) { return concat(multi(a, b - 1), a); } node z = multi(a, b / 2); return concat(z, z); } const int N = 100010; node prec[N]; node big_seq(int n7, int n6, int k) { node res = seq(n7, n6, k - 1); for (int i = k - 2; i >= 0; i--) { res = concat(prec[i], res); } return res; } char s[N]; int pos; node solve_exp() { int start = pos; int v7 = 0; int v6 = 0; while ('0' <= s[pos] && s[pos] <= '9') { v7 = mul(v7, 10); add(v7, s[pos] - '0'); v6 = mul(v6, 10, MOD - 1); add(v6, s[pos] - '0', MOD - 1); pos++; } int len_v = pos - start; if (s[pos] == '+') { pos++; return concat({v7, len_v}, solve_exp()); } if (s[pos] == '-') { pos++; int start2 = pos; int w7 = 0; int w6 = 0; while ('0' <= s[pos] && s[pos] <= '9') { w7 = mul(w7, 10); add(w7, s[pos] - '0'); w6 = mul(w6, 10, MOD - 1); add(w6, s[pos] - '0', MOD - 1); pos++; } int len_w = pos - start2; add(v7, MOD - 1); add(v6, (MOD - 1) - 1, MOD - 1); node v = big_seq(v7, v6, len_v); node w = big_seq(w7, w6, len_w); int diff = w.len - v.len; if (diff < 0) { diff += MOD - 1; } int real_value = w.value; add(real_value, MOD - mul(v.value, power(10, diff))); int real_len = w.len; add(real_len, (MOD - 1) - v.len, MOD - 1); if (s[pos] == '+') { pos++; return concat({real_value, real_len}, solve_exp()); } return {real_value, real_len}; } if (s[pos] == '(') { int finish = pos; pos++; node z = solve_exp(); node res = {0, 0}; for (int i = start; i < finish; i++) { res = multi(res, 10); if (s[i] != '0') { res = concat(res, multi(z, s[i] - '0')); } } pos++; if (s[pos] == '+') { pos++; return concat(res, solve_exp()); } return res; } return {v7, len_v}; } int main() { /* int real = 0; for (int i = 1; i <= 12345; i++) { real = mul(real, i <= 9 ? 10 : (i <= 99 ? 100 : (i <= 999 ? 1000 : (i <= 9999 ? 10000 : 100000)))); add(real, i); } printf("%d\n", real);*/ int v7 = 0; int v6 = 0; for (int k = 0; k < N; k++) { v7 = mul(v7, 10); add(v7, 9); v6 = mul(v6, 10, MOD - 1); add(v6, 9, MOD - 1); prec[k] = seq(v7, v6, k); } scanf("%s", s); pos = 0; node res = solve_exp(); printf("%d\n", res.value); return 0; }
Related posts:
Resource Distribution
Sieve of Eratosthenes
Businessmen Problems
Middle Class
Bracket Sequence
New Year and Three Musketeers
Aroma's Search
LCM Challenge
Koala and Lights
Suns and Rays
Uniqueness
Finding articulation points in a graph in $O(N+M)$
Maximum flow - Dinic's algorithm
New Year and North Pole
Diverse Matrix
Fox and Box Accumulation
New Year and the Mallard Expedition
Wrong Answer on Test 233 (Hard Version)
T-shirt buying
Function
Awesome Substrings
Wrong Subtraction
Double Permutation Inc
Dividing Kingdom II
Deduction Queries
Noise Level
Read Time
Sum of Nestings
Median on Segments
Envy
Point location in O(log n)
Optimal Polygon Perimeter