Search Insert Position 60

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.

Example

[1,3,5,6], 5 → 2

[1,3,5,6], 2 → 1

[1,3,5,6], 7 → 4

[1,3,5,6], 0 → 0

Challenge

O(log(n)) time

Solution

二分搜索，找到第一个大于等于target的数。

代码如下：

public class Solution {
    /** 
     * param A : an integer sorted array
     * param target :  an integer to be inserted
     * return : an integer
     */
    public int searchInsert(int[] A, int target) {
        // write your code here
        if(A == null || A.length == 0){
            return 0;
        }

        int start = 0;
        int end = A.length - 1;

        while (start + 1 < end){
            int mid = start + (end - start)/2;
            if (A[mid] == target){
                return mid;
            }else if (A[mid] < target){
                start = mid;
            }else{
                end = mid;
            }
        }

        if (A[start] >= target){
            return start;
        }else if (A[end] < target){
            return end + 1;
        }else{
            return end;
        }
    }
}