LeetCode刷题笔录 Search Insert Position-优快云博客

本文介绍了一种在已排序数组中查找目标值或确定其插入位置的算法。通过两种方法实现：线性搜索与二分搜索。线性搜索简单直接但效率较低；二分搜索则更为高效，适用于大型数据集。

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

线性搜索最简单了：

public class Solution {
    public int searchInsert(int[] A, int target) {
        for(int i = 0; i < A.length; i++){
            if(A[i] < target)
                continue;
            else 
                return i;
        }
        return A.length;
    }
}

改进一下，可以用binary search。只要注意一下什么时候该返回什么值就行了，比较简单。

public class Solution {
    public int searchInsert(int[] A, int target) {
       return searchInsertBinary(A, 0, A.length - 1, target);
    }
    
    public int searchInsertBinary(int[] array, int low, int high, int target){
        int mid = (low + high) / 2;
        if(array[low] > target)
            return low;
        if(array[high] < target)
            return high + 1;
        if(array[mid] == target)
            return mid;
        else if(array[mid] > target)
            return searchInsertBinary(array, low, mid, target);
        else 
            return searchInsertBinary(array, mid + 1, high, target);
            
    }
}