LeetCode: Search Insert Position

思路：二分搜索，对于当前元素A[mid]，如果A[mid] > target，则应该从left 到 mid-1进行搜索，但是如果A[mid-1] < target 则插入位置就是mid这里，返回mid值，注意向左搜到mid==0时，还没有确定好位置，就应该返回0，并入到一起就是return mid，右边情况的分析类似。

code:

class Solution {
public:
    int searchInsert(int A[], int n, int target) {
        int left = 0, right = n-1;
        while(left <= right){
            int mid = (left + right)>>1;
            if(A[mid] == target)return mid;
            else if(A[mid] > target){
                if(mid == 0 || A[mid-1] < target)return mid;
                right = mid - 1;
            }
            else{
                if(mid == n-1 || A[mid+1] > target)return mid+1;
                left = mid + 1;
            }
        }
    }
};