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SearchInRotatedSortedArray.java
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SearchInRotatedSortedArray.java
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package oj.leetcode;
/**
* 33. Search in Rotated Sorted Array
*/
public class SearchInRotatedSortedArray {
/**
* AC
* 耗时6ms
* 先找到旋转点,然后使用二分查找在左右部分进行查找目标
*/
public static int search(int[] nums, int target) {
if (nums == null || nums.length <= 0)
return -1;
int lo = 0, hi = nums.length - 1;
int mid = 0;
while (lo < hi) {
mid = (lo + hi) >>> 1; // 应该比 /2 要快
if (nums[mid] > nums[hi])
lo = mid + 1;
else hi = mid;
}
// get here, lo==hi
// this is the rotate point
int rotate = lo;
// binary search in left part
lo = 0;
hi = rotate - 1;
while (lo <= hi) {
mid = (lo + hi) >>> 1;
if (nums[mid] == target)
return mid;
else if (nums[mid] > target)
hi = mid - 1;
else lo = mid + 1;
}
// binary search in right part
lo = rotate;
hi = nums.length - 1;
while (lo <= hi) {
mid = (lo + hi) >>> 1;
if (nums[mid] == target)
return mid;
else if (nums[mid] > target)
hi = mid - 1;
else lo = mid + 1;
}
return -1;
}
public static void main(String[] args) {
int a[] = {4, 5, 6, 7, 0, 1, 2};
System.out.println(search(a, 0));
int b[] = {6, 7, 0, 1, 2, 5};
System.out.println(search(b, 0));
int c[] = {4};
System.out.println(search(c, 4));
}
}