LintCode Binary Search

class Solution {
public:
/**
* @param nums: The integer array.
* @param target: Target number to find.
* @return: The first position of target. Position starts from 0.
*/
int binarySearch(vector<int> &array, int target) {
// write your code here
long len = array.size();
long lo = 0;
long hi = len;
while (lo < hi) {
long mid = (lo + hi) / 2;
if (array[mid] < target) {
lo = mid + 1;
} else {
hi = mid;
}
}

return (lo == len || array[lo] != target) ? -1 : lo;
}
};