[leetcode 35] Search Insert Position

1 题目：

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

2 思路：

变相的二分搜索

注意处理边界和溢出情况

 

3 代码：

    public int searchInsert(int[] nums, int target) {
        // pre handle
        if(nums[0] > target){
            return 0;
        }
        if(nums[nums.length-1] < target){
            return nums.length;
        }
        
        /* again, binary search */
        int pre = 0;
        int after = nums.length-1;
        while(pre<=after){
            int mid = pre + ((after-pre)>>1);
            if(nums[mid]==target){
                return mid;
            }else if(nums[mid]<target){
                if(mid < nums.length-1 && nums[mid+1]>target){
                    return mid+1;
                }
                pre = mid+1;
            }else if (nums[mid]>target){
                if(mid>0 && nums[mid-1]<target){
                    return mid;
                }
                after = mid-1;
            }
        }
        
        // will never reach here
        return 0;
    }