Leetcode problem no. :1513.
1513. Number of Substrings With Only 1s GENERAL APPROACH We scan the string once from left to right.We count how many consecutive ‘1’ characters appear in a row. => (k⋅(k+1))/2 Then reset the counter. At the end, we add the contribution of the last streak. This approach is optimal with O(n) time and O(1) space. … Read more