Search Insert Position

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

同样是在有序数组中查找一个目标元素，这种情况我们一般都用二分查找法。这道题目比较简单，用二分法找到目标元素就直接返回当然元素下标；如果没有找到，当二分查找结束时，也就是left指针大于right指针后，此时left指针恰好为要插入的位置。代码如下：

public class Solution {
    public int searchInsert(int[] nums, int target) {
        if(nums == null || nums.length == 0) return 0;
        int l = 0; 
        int r = nums.length - 1;
        while(l <= r) {
            int m = l + (r - l) / 2;
            if(nums[m] == target) {
                return m;
            } else if(nums[m] > target) {
                r = m - 1;
            } else {
                l = m + 1;
            }
        }
        return l;
    }
}