二分搜索算法（递归和非递归实现）

//循环迭代方法
int binIteration(int a[],int low,int high,int key){
if(low>high) return -1;
if(a[high] < key || a[low] > key) return -1;
while(low<=high){
int mid=(low+high)/2;
if(a[mid] == key) return mid;
else if(a[mid] > key) high = mid-1;
else low = mid+1;
}
return -1;
}

//递归方法
int binRecursion(int a[],int low,int high,int key){
if(low > high) return -1;
if(a[high] < key || a[low] >key) return -1;
int mid=(low+high)/2;
if(a[mid] == key) return mid;
else if(a[mid] > key) return binRecursion(a,low,mid-1,key);
else return binRecursion(a,mid+1,high,key);
}