# Pattern

Solve Problem by Patterns at [Algomaster](https://algomaster.io/practice/dsa-patterns) | [thita](https://thita.ai/dsa-patterns-sheet) | 

![](/files/w0v0JhXtGam3efbNsdKV)

### **Prefix Sum** : 

The Prefix Sum pattern involves preprocessing an array to create a new array where each element at index i represents the sum of all elements from the start up to i. This allows for O(1) sum queries on any sub array. We can use this in following scenario :- 

1. Multiple sum queries on sub arrays
2. Finding sub arrays with a target sum
3. Calculating cumulative totals

References 

* <https://x.com/ashishps_1/status/2012864271773016266>
* <https://blog.algomaster.io/p/15-leetcode-patterns>&#x20;
* <https://leetcode.com/discuss/post/1326900/graph-algorithms-problems-to-practice-by-9u6j/>
* <https://leetcode.com/discuss/post/655708/graph-for-beginners-problems-pattern-sam-06fb/>&#x20;

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