Given a list of n numbers from 1 to n-1, with one of the numbers repeated. Devise a method to determine which number is repeated

The sum of the numbers 1 to n-1 is (n)(n-1)/2. Add the numbers on the list, and subtract (n)(n-1)/2. The result is the number that has been repeated.

See also

• Asymptotic Notation
• Growth Rate - The Importance of Asymptotics
• For a Given node of a binary tree, print the K distance nodes.
• Find the distance between 2 nodes in Binary Tree
• Find the distance between 2 nodes in Binary Tree