C++ Program for Queries for rotation and Kth character of the given string in constant time
Last Updated :
09 Jun, 2022
Given a string str, the task is to perform the following type of queries on the given string:
- (1, K): Left rotate the string by K characters.
- (2, K): Print the Kth character of the string.
Examples:
Input: str = “abcdefgh”, q[][] = {{1, 2}, {2, 2}, {1, 4}, {2, 7}}
Output:
d
e
Query 1: str = “cdefghab”
Query 2: 2nd character is d
Query 3: str = “ghabcdef”
Query 4: 7th character is e
Input: str = “abc”, q[][] = {{1, 2}, {2, 2}}
Output:
a
Approach: The main observation here is that the string doesn’t need to be rotated in every query instead we can create a pointer ptr pointing to the first character of the string and which can be updated for every rotation as ptr = (ptr + K) % N where K the integer by which the string needs to be rotated and N is the length of the string. Now for every query of the second type, the Kth character can be found by str[(ptr + K – 1) % N].
Below is the implementation of the above approach:
C++
#include <bits/stdc++.h>
using namespace std;
#define size 2
void performQueries(string str, int n,
int queries[][size], int q)
{
int ptr = 0;
for (int i = 0; i < q; i++) {
if (queries[i][0] == 1) {
ptr = (ptr + queries[i][1]) % n;
}
else {
int k = queries[i][1];
int index = (ptr + k - 1) % n;
cout << str[index] << " ";
}
}
}
int main()
{
string str = "abcdefgh";
int n = str.length();
int queries[][size] = { { 1, 2 }, { 2, 2 },
{ 1, 4 }, { 2, 7 } };
int q = sizeof(queries) / sizeof(queries[0]);
performQueries(str, n, queries, q);
return 0;
}
|
Time Complexity: O(Q), Where Q is the number of queries.
Auxiliary Space: O(1)
Please refer complete article on Queries for rotation and Kth character of the given string in constant time for more details!
Like Article
Suggest improvement
Share your thoughts in the comments
Please Login to comment...