二分查找

int binarySearch(int[] a, int value)
{
int low = 0;
int high = a.length - 1;
int mid;
while (low <= high)
{
mid = (low + high) / 2;//mid=low+(high-low)/2;
if (a[mid] < value)
{
low = mid + 1;
}
else if (a[mid] > value)
{
high = mid - 1;
}
else
{
return mid;
}
}
return -1;//错误
}


int binarySearchRecursive(int[] a, int x, int low, int high)
{
if (low > high)
return -1;//错误
int mid = (low + high) / 2;
if (a[mid] < x)
{
return binarySearchRecursive(a, x, mid + 1, high)l;
}
else if (a[mid]>x)
{
return binarySearchRecursive(a, x, low, mid - 1);
}
else
{
return mid;
}
}