学步园

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 

折半查找，两分支判断。

此算法在leetcode上实际执行时间为10ms。

class Solution {

public:
    int searchInsert(int A[], int n, int target) {
        if (!n) return -1;
        if (target > A[n-1]) return n;

        int low = 0, high = n-1;
        while (low < high) {
                const int mid = low + (high - low) / 2;
                if (A[mid] < target)
                        low = mid + 1;
                else
                        high = mid;
        }

        return low;
    }

};