The final common value of an array equals its GCD

Article explains algorithm to find final equal value when replacing larger of two unequal array elements by their difference; answer equals the GCD. Two approaches are presented: a naive max-heap simulation and an efficient GCD method. Since each operation preserves the array's overall GCD, the final common value is simply that GCD, computable in O(n log max). The article includes code in C++, Java, Python, C#, and JavaScript. The naive heap method is useful for illustration, while the GCD approach is optimal for large arrays.