Problem Description
In a string s of lowercase letters, these letters form consecutive groups of the same character. A group is considered large if it has 3 or more characters. Return the intervals of every large group sorted in increasing order by start index.
Key Insights
- A group is formed by consecutive identical characters.
- A group is defined by its start and end indices in the string.
- Large groups have a length of 3 or more characters.
- We need to traverse the string once to identify groups and their sizes.
Space and Time Complexity
Time Complexity: O(n), where n is the length of the string since we traverse it once.
Space Complexity: O(k), where k is the number of large groups we find, as we store their intervals.
Solution
To solve this problem, we can use a single pass through the string to identify groups of consecutive characters. We maintain two pointers, one for the start of a group and another to find the end of that group. If the length of the group is 3 or more, we store its start and end indices. Finally, we return the list of large groups.