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

解题分析：就是普通的二分搜索，加了一点点改进，多一个判断步奏。

class Solution {
public:
    int searchInsert(int A[], int n, int target) {
        int low = 0;
        int high = n - 1;
        while(low <= high) {
            int middle = (low + high) / 2;
            if(A[middle] == target) return middle;
            else if(A[middle] < target) {
                 if(A[middle+1] > target)  return middle+1;
                 else low = middle + 1;
                 }
            else if(A[middle] > target) {
                 if(A[middle-1] < target)  return middle;
                 else high = middle - 1;
                 }
        }
    }
};

LeetCode-Search Insert Position