public int Search(ArrayReader reader, int target)
{
int left = 0;
int right = 1;
while(reader.get(right) < target)
{
left = right;
right <<= 1;
}
while(left <= right)
{
var mid = left + ((right - left) >> 1);
var temp = reader.get(mid);
if (temp == target)
{
return mid;
}
else if (temp < target)
{
left = mid + 1;
}
else
{
right = mid - 1;
}
}
return -1;
}
/**
* @param reader: An instance of ArrayReader can read number by index.
* @param target: An integer
* @return : An integer which is the index of the target number
*/
public int SearchBigSortedArray(ArrayReader reader, int target)
{
// Algorithm:
// 1. get the index that ArrayReader.get(index) >= target in
// O(logk)
// 2. Binary search the target between 0 and index
int index = 1;
while (reader.get(index - 1) < target)
{
index = index * 2;
}
int start = 0, end = index - 1;
while (start + 1 < end)
{
int mid = start + (end - start) / 2;
if (reader.get(mid) < target)
{
start = mid;
}
else
{
end = mid;
}
}
if (reader.get(start) == target)
{
return(start);
}
if (reader.get(end) == target)
{
return(end);
}
return(-1);
}