{"id":924,"date":"2025-08-20T13:05:52","date_gmt":"2025-08-20T07:35:52","guid":{"rendered":"https:\/\/codeanddebug.in\/blog\/?p=924"},"modified":"2025-08-20T13:24:04","modified_gmt":"2025-08-20T07:54:04","slug":"binary-subarrays-with-sum","status":"publish","type":"post","link":"https:\/\/codeanddebug.in\/blog\/binary-subarrays-with-sum\/","title":{"rendered":"Binary Subarrays With Sum | Leetcode 930 | Optimal Prefix\/Sliding Window Trick"},"content":{"rendered":"\n

The problem \u201cBinary Subarrays With Sum\u201d<\/strong> asks to count the number of contiguous subarrays in a binary array nums<\/code> whose sum equals a given goal<\/strong>. Because the array is binary (only 0s and 1s), we can exploit special properties to achieve an O(n)<\/strong> solution using a clever at-most<\/strong> trick.<\/p>\n\n\n\n

Here’s the [Problem Link<\/span><\/mark><\/a><\/strong>] to begin with.<\/p>\n\n\n\n

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Given a binary array nums<\/code> and an integer goal<\/code>, return the number of non-empty subarrays<\/strong> with a sum<\/em> goal<\/code>.<\/p>\n\n\n\n

A subarray<\/strong> is a contiguous part of the array.<\/p>\n\n\n\n

Example 1:<\/strong><\/p>\n\n\n\n

Input:<\/strong> nums = [1,0,1,0,1], goal = 2
Output:<\/strong> 4
Explanation:<\/strong> The 4 subarrays are bolded and underlined below:
[1,0,1<\/strong>,0,1]
[1,0,1,0<\/strong>,1]
[1,0,1,0,1<\/strong>]
[1,0,1,0,1<\/strong>]<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
Input:<\/strong> nums = [0,0,0,0,0], goal = 0
Output:<\/strong> 15<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n