LeetCode -- Search Insert Position

Question:

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

 

Analysis:

给出一个排好序的数组和一个目标值，如果数组中含有这个值则返回他的index；若不存在target，则返回应该插入额位置。

思路：

二分查找。定义两个指针，分情况讨论。注意边界情况。

 

Answer:

public class Solution {
    public int searchInsert(int[] nums, int target) {
        if(nums == null || nums.length == 0)
                return -1;
        int i = 0, j = nums.length - 1;
        
        if(nums[i] > target)
                return 0;
        if(nums[j] < target)
                return j + 1;
        
        while(true) {
                int mid = i + (j - i) / 2;
                if(mid == i && nums[i] < target && nums[j] > target) {
                    return j;
                }
                if(mid == i && nums[j] == target) {
                    return j;
                }
                if(nums[mid] == target)
                    return mid;
                if(nums[mid] > target) {
                    j = mid;
                }
                if(nums[mid] < target) {
                    i = mid;
                }
        }
    }
}