34. Search Insert Position

weixin_30568591

于 2013-09-04 09:48:00 发布

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/ycled/p/3300377.html

本文介绍了一个算法问题：在一个已排序的数组中查找指定值的索引，若不存在则返回其应插入的位置。该文提供了使用二分搜索法解决此问题的Java实现。

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

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BST

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public class Solution {
    public int searchInsert(int[] A, int target) {
        
        return helper(A, target, 0, A.length-1);
        
    }
      
    
    private int helper(int[] A, int target, int l, int r){
        
        // not found
        if(l > r) return l;   
            
        // bst 
        int mid = l + (r-l) / 2;
      
        if(A[mid] == target){   
            // found
            return mid;
                    
        }else if(A[mid] > target){
            // search left
            return helper(A, target, l, mid-1);
            
        }else{
            // search right
            return helper(A, target, mid+1, r);        
        }
    }
}