问题叙述性说明：
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
假设小于，则返回medium。
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
原文：http://www.cnblogs.com/mengfanrong/p/5041107.html