标签：style blog http color os io for ar
Search in Rotated Sorted Array
Suppose a sorted array is rotated at some pivot unknown to you beforehand.
(i.e.,
0 1 2 4 5 6 7might become4 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.
二分查找的变形
算法思路：
a[mid] == target return mid;
a[mid] < target 分为两种情况
1. a[mid]和target在同半边，begin = mid + 1
2. a[mid]和target在不同的半边，则a[mid]肯定在后面，target在前半边，因此往前找end = mid - 1;
a[mid] > target同理
1. a[mid]和target在同半边，end = mid - 1;
2. a[mid]和target在不同的半边，则a[mid]肯定在前面，target在后半边，因此往前找begin = mid + 1;
代码如下：
1 public class Solution { 2 public int search(int[] a, int target) { 3 if(a == null || a.length == 0) return -1; 4 int begin = 0, end = a.length - 1; 5 while(begin <= end){ 6 int mid = (begin + end) >> 1; 7 if(a[mid] == target){ 8 return mid; 9 }else if(a[mid] < target){ 10 if(a[mid] < a[begin] && target >= a[begin]){ 11 end = mid - 1; 12 }else{ 13 begin = mid + 1; 14 } 15 }else{ 16 if(a[mid] >= a[begin] && target < a[begin]){ 17 begin = mid + 1; 18 }else{ 19 end = mid - 1; 20 } 21 } 22 } 23 return -1; 24 } 25 }
[leetcode]Search in Rotated Sorted Array,布布扣,bubuko.com
[leetcode]Search in Rotated Sorted Array
标签：style blog http color os io for ar
原文地址：http://www.cnblogs.com/huntfor/p/3901303.html
