Orig Description
Score : 500 points
Problem StatementYou are given a string S of length N consisting of lowercase English letters.
Process Q queries of the following two types:
Type 1: change the i_q-th character of S to c_q. (Do nothing if the i_q-th character is already c_q.)
Type 2: answer the number of different characters occurring in the substring of S between the l_q-th and r_q-th characters (inclusive).
Constraints
N, Q, i_q, l_q, and r_q are integers.
S is a string consisting of lowercase English letters.
c_q is a lowercase English letter.
1 \leq N \leq 500000
1 \leq Q \leq 20000
|S| = N
1 \leq i_q \leq N
1 \leq l_q \leq r_q \leq N
There is at least one query of type 2 in each testcase.
InputInput is given from Standard Input in the following format:
N
S
Q
Query_1
\vdots
Query_Q
Here, Query_i in the 4-th through (Q+3)-th lines is one of the following:
1 i_q c_q
2 l_q r_q
OutputFor each query of type 2, print a line containing the answer.
Sample Input 17
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7
Sample Output 13
1
5
In the first query, cdbb contains three kinds of letters: b , c , and d, so we print 3.
In the second query, S is modified to abcdzbd.
In the third query, a contains one kind of letter: a, so we print 1.
In the fourth query, S is modified to abcazbd.
In the fifth query, S does not change and is still abcazbd.
In the sixth query, abcazbd contains five kinds of letters: a, b, c, d, and z, so we print 5.
Extracted Specification
An integer N (1 ≤ N ≤ 500000), representing some quantity or size.
A string S of length N, consisting of lowercase English letters.
An integer Q (1 ≤ Q ≤ 20000), representing some number of queries.
A list of Q queries, where each query is one of the following two types:
1. "1 i_q c_q" - where i_q (1 ≤ i_q ≤ N) is an integer and c_q is a lowercase English letter.
2. "2 l_q r_q" - where l_q and r_q (1 ≤ l_q ≤ r_q ≤ N) are integers.
### Example Input:
```
7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7
```
### Function Signature:
Write a function f(N, S, Q, queries) that takes in the input.
def f(N: int, S: str, Q: int, queries: List[str]):
'''
N: an integer
S: a string
Q: an integer
queries: a list of strings
'''
Test Case Generator
Certainly! Here’s a test case generator for the given problem statement:
```python
import random
import string
def generate_test_case():
# Generate random values for N and Q within their respective constraints.
N = random.randint(1, 500000)
Q = random.randint(1, 20000)
# Generate a random string S of length N consisting of lowercase English letters.
S = ''.join(random.choices(string.ascii_lowercase, k=N))
# Initialize a list to store the queries
queries = []
# Ensure at least one query of type 2
type2_query = f"2 {random.randint(1, N)} {random.randint(1, N)}"
# Correct the order of l_q and r_q if needed
l_q, r_q = map(int, type2_query.split()[1:])
if l_q > r_q:
l_q, r_q = r_q, l_q
type2_query = f"2 {l_q} {r_q}"
queries.append(type2_query)
# Generate the remaining Q-1 queries
for _ in range(Q - 1):
query_type = random.choice([1, 2])
if query_type == 1:
i_q = random.randint(1, N)
c_q = random.choice(string.ascii_lowercase)
queries.append(f"1 {i_q} {c_q}")
else:
l_q = random.randint(1, N)
r_q = random.randint(1, N)
if l_q > r_q:
l_q, r_q = r_q, l_q
queries.append(f"2 {l_q} {r_q}")
return N, S, Q, queries
# Example of generating a test case
if __name__ == "__main__":
N, S, Q, queries = generate_test_case()
print(N)
print(S)
print(Q)
for query in queries:
print(query)
```
### Explanation:
1. **N**: A random integer between 1 and 500,000.
2. **S**: A random string of lowercase letters of length N.
3. **Q**: A random integer between 1 and 20,000.
4. **Queries**: A list of Q queries.
- **Type 1 Query**: Generates a query of the form `1 i_q c_q` where `1 <= i_q <= N` and `c_q` is a random lowercase letter.
- **Type 2 Query**: Generates a query of the form `2 l_q r_q` where `1 <= l_q <= r_q <= N`. Ensures `l_q` is not greater than `r_q`.
The generator ensures there is at least one query of type 2 by creating it first, and then randomly generating the remaining queries. It also ensures that the ranges in type 2 queries are valid.
Extract Arguments
def extract_arguments(fh):
N = int(fh.readline().strip())
S = fh.readline().strip()
Q = int(fh.readline().strip())
queries = []
for _ in range(Q):
query = fh.readline().strip().split()
if query[0] == '1':
queries.append((1, int(query[1]), query[2]))
else:
queries.append((2, int(query[1]), int(query[2])))
return N, S, Q, queries