How to find second largest number in an array in Java?

Question

I\'m just practicing some MIT java assignments. But, I\'m not sure how to find the second largest number. http://ocw.csail.mit.edu/f/13

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Answer 1

Instead of resorting to sorting the array, you can simply do the following:

• Keep a largestValue and a secondLargestValue
• Loop through the entire array once, for each element:
  • Check to see if the current element is greater than largestValue:
    • If so, assign largestValue to secondLargestValue, then assign the current element to largestValue (think of it as shifting everything down by 1)
    • If not, check to see if the current element is greater than secondLargestValue
      • If so, assign the current element to secondLargestValue
      • If not, do nothing.

O(n) run time

O(1) space requirement