33. Search in Rotated Sorted Array (JAVA)

最新推荐文章于 2022-05-06 14:52:45 发布

转载最新推荐文章于 2022-05-06 14:52:45 发布 · 165 阅读

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原文链接：http://www.cnblogs.com/qionglouyuyu/p/10811963.html

博客介绍了实现下一个排列的需求，即把数字重新排列成字典序中下一个更大的排列，若无法实现则排成最小顺序，且要求原地替换、仅用常量额外内存，还提到由O(log n)想到二分法。

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).

The replacement must be in-place and use only constant extra memory.

Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.

1,2,3 → 1,3,2
3,2,1 → 1,2,3
1,1,5 → 1,5,1

O(log n) =>想到二分法

class Solution {
    public int search(int[] nums, int target) {
        return binarySearch(nums,target,0,nums.length-1); 
        
    }
    public int binarySearch(int[] nums, int target, int left, int right){
        if(left > right) return -1; //not found
        
        int mid = left + ((right-left)>>1);
        if(target == nums[mid]) return mid; //found
        
        if(nums[mid] < nums[left]){//rotate in the left part
            if(target < nums[mid] || target >nums[right]){ //target in the left part
                return binarySearch(nums,target,left,mid-1);
            }
            else{ //target in the right part
                return binarySearch(nums,target,mid+1,right);
            }
        }
        else if(nums[mid] > nums[right]){ //rotate in the right part
            if(target > nums[mid] || target < nums[left]) {//target in the right part
                return binarySearch(nums,target,mid+1,right);
            }
            else{//target in the left part
                return binarySearch(nums,target,left,mid-1);
            }
        }
        else{ //no rotate
            if(target < nums[mid]){
                return binarySearch(nums,target,left,mid-1);
            }
            else{
                return binarySearch(nums,target,mid+1,right);
            }
        }
                     
    }
}

转载于:https://www.cnblogs.com/qionglouyuyu/p/10811963.html