Find the minimum in a sorted and rotated Array

FindMinRotatedSortedArray.cs

//Assumes there are no duplicate 
//O(log n)
public int FindMinRotatedArray(int[] ar){
  
  int n = ar.Length;
  int lo = 0;
  int hi = n - 1;
  while(lo <= hi){
    
    if(ar[lo] <= ar[hi]) // (sub) array is already sorted, yay!
      return ar[lo];
    
    int mid = lo + (hi - lo)/2; //prevent int overflow, assumes all are positive
    int next = (mid + 1) % n; //modulus is needed if mid is the start/end of the array
    int prev = (mid + n - 1) % n;
    
    //check if mid is the min. Both it's previous and next are higher
    if((ar[mid] <=ar[prev])&&(ar[mid] <=ar[next]))
      return ar[mid];
    
    //figure out where is the dip
    if(ar[mid] <= ar[lo]) 
      hi = mid - 1; //the dip is in the half left side
    else 
      lo = mid + 1;
  }
  
  return -1;
}