類似問題：迴圈有序陣列/旋轉陣列的最小值 《劍指offer》P66

#include <iostream>
using namespace std;

// 參考 http://blog.sina.com.cn/s/blog_a2498b5b01014bsg.html
// 參考 http://blog.csdn.net/qq_33724710/article/details/51200889

// 二分查詢
int binarySearch(int a[],int low,int high,int value)
{
  if(low>high)
    return -1;

  int mid=(low+high)/2;
  if(value==a[mid])
    return mid;
  else if(value>a[mid])
    return binarySearch(a,mid+1,high,value);
  else
    return binarySearch(a,low,mid-1,value);
}

// 遞迴查詢
int searchRecursively(int a[],int low,int high,int value)
{
  int mid=(low+high)/2;

  if(a[mid]>a[low])       //左有序
  {
    if(a[low]<=value && value<=a[mid] )        //value在左邊，直接二分查詢
      return binarySearch(a,low,mid,value);
    else                                       //value在右邊，遞迴查詢
      return searchRecursively(a,mid+1,high,value);
  }
  else                    //右有序
  {
    if(a[mid]<=value && value<=a[high])
      return binarySearch(a,mid,high,value);
    else
      return searchRecursively(a,low,mid-1,value);
  }
}

// 迴圈查詢
int searchCircularly(int* nums, int numsSize, int target)
{
  int first = 0;
  int last = numsSize - 1;

  while (first <= last) {  
    int mid = (last - first) / 2 + first;
    if (*(nums + mid) == target)
      return mid;
    else if (*(nums + first) <= *(nums + mid)) {
      if (*(nums + first) <= target && target < *(nums + mid))
        last = mid - 1;
      else
        first = mid + 1;
    }
    else {
      if (*(nums + mid) < target && target <= *(nums + last))
        first = mid + 1;
      else
        last = mid - 1;
    }
  }
  return -1;
}

int main()
{
  int a[]={3,4,5,6,7,8,9,0,1,2};

  cout<<searchRecursively(a,0,9,0)<<endl;
  cout<<searchCircularly(a,9,0)<<endl;

  int ttt = 0;
  return 0;
}