问题描述：

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You may assume no duplicates in the array.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

代码：

int head = 0;
    int tail = n-1;
    int medium;
    while(head <= tail)
    {
        medium = (head + tail) / 2;
        if(A[medium] == target)
            return medium;
        /*if(tail - head == 1 && A[tail] != target && A[head] != target)
        {
            if(target > A[tail])
                return tail + 1;
            else if(target > A[head] && target < A[tail])
                return tail;
            else
                return head;
        }*/
        if(A[medium] > target)
            tail = medium - 1;
        if(A[medium] < target)
            head = medium + 1;
    }
    if(head == tail)
    {
        if(target > A[tail])
            return tail+1;
        else
            return head;
    }

LeetCode:Search Insert Position