leetcode------Search in Rotated Sorted Array

标题： Search in Rotated Sorted Array
通过率： 28.9%
难度： 难

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

这个题目是升级版的难度定为中等，我再做这个升级版时不知道什么旋转排序数组，然后来先做这个版本，然后我才弄明白，这种类型有两种情况

1.    4567012中间为7且   start=4<7,那么target如果在4-7之间的或者在7以外

2.45670123中间位置为0 且 start=4>0，那么target在4-0之间或者0以外。

直接看代码，最后一个else操作是start++  看一个例子 【1，3】target=3.当mid=0时 start=0 ，mid对应的元素和start对应的元素是相等，但是又不等于target

代码如下：

 1 public class Solution {
 2     public int search(int[] A, int target) {
 3         int start=0,end=A.length-1,mid=0;
 4         while(start<=end){
 5             mid=(start+end)/2;
 6             if(A[mid]==target)return mid;
 7             if(A[start]<A[mid]){
 8                 if((target<A[mid])&&(target>=A[start]))
 9                     end=mid-1;
10                     else start=mid+1;
11             }
12             else if(A[start]>A[mid]){
13                 if((target<A[mid])||(target>=A[start]))
14                     end=mid-1;
15                     else start=mid+1;
16             }
17             else start++;
18         }
19         return -1;
20     }
21 }

python：

 1 class Solution:
 2     # @param A, a list of integers
 3     # @param target, an integer to be searched
 4     # @return an integer
 5 
 6     def search(self, A, target):
 7         left = 0
 8         right = len(A) - 1
 9 
10         while left <= right:
11             mid = (left + right) >> 1
12             if target == A[mid]:
13                 return mid
14             # print mid, A[mid], left, A[left], right, A[right], '..',
15             if A[left] <= A[mid]:
16                 if A[left] <= target and target <= A[mid]:
17                     right = mid - 1
18                 else:
19                     left = mid + 1
20             else:
21                 if A[mid] < target and target <= A[right]:
22                     left = mid + 1
23                 else:
24                     right = mid - 1
25         return -1

 

posted @ 2015-02-12 11:27  pku_smile  阅读(140)  评论(0)  编辑  收藏  举报