Repository navigation
Expand file tree
/
Copy path_33_search.java
More file actions
108 lines (103 loc) · 3.52 KB
/
Copy path_33_search.java
File metadata and controls
108 lines (103 loc) · 3.52 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
package pp.arithmetic.leetcode;
/**
* Created by wangpeng on 2018/9/12.
* 33. 搜索旋转排序数组
* <p>
* 假设按照升序排序的数组在预先未知的某个点上进行了旋转。
* <p>
* ( 例如，数组 [0,1,2,4,5,6,7] 可能变为 [4,5,6,7,0,1,2] )。
* <p>
* 搜索一个给定的目标值，如果数组中存在这个目标值，则返回它的索引，否则返回 -1 。
* <p>
* 你可以假设数组中不存在重复的元素。
* <p>
* 你的算法时间复杂度必须是 O(log n) 级别。
* <p>
* 示例 1:
* <p>
* 输入: nums = [4,5,6,7,0,1,2], target = 0
* 输出: 4
* 示例 2:
* <p>
* 输入: nums = [4,5,6,7,0,1,2], target = 3
* 输出: -1
*
* @see <a href="https://leetcode-cn.com/problems/search-in-rotated-sorted-array/description/">search-in-rotated-sorted-array</a>
*/
public class _33_search {
public static void main(String[] args) {
int search = search(new int[]{4, 5, 6, 7, 0, 1, 2}, 0);
System.out.println(search);
int search1 = search(new int[]{4, 5, 6, 7, 0, 1, 2}, 3);
System.out.println(search1);
}
public static int search(int[] nums, int target) {
if (nums == null || nums.length == 0) {
return -1;
}
int start = 0;
int end = nums.length - 1;
int middle;
while (start <= end) {
middle = (start + end) / 2;
if (target == nums[middle]) {
return middle;
} else if (target < nums[middle]) {
if (nums[start] < nums[middle]) {
//一定是递增区间
if (target > nums[start]) {
end = middle - 1;
} else if (target < nums[start]) {
start = middle + 1;
} else {
return start;
}
} else if (nums[start] > nums[middle]) {
//一定是旋转区间
end = middle - 1;
} else {
start = middle + 1;
}
} else if (target > nums[middle]) {
if (nums[end] > nums[middle]) {
//一定是递增区间
if (target > nums[end]) {
end = middle - 1;
} else if (target < nums[end]) {
start = middle + 1;
} else {
return end;
}
} else if (nums[end] < nums[middle]) {
//包含旋转区间
start = middle + 1;
} else {
end = middle - 1;
}
}
}
return -1;
}
public static int searchByOther(int[] nums, int target) {
if (nums == null || nums.length == 0) return -1;
int start = 0, end = nums.length - 1;
while (start < end) {
int mid = (start + end) / 2;
if (nums[mid] > nums[end]) { // eg. 3,4,5,6,1,2
if (target > nums[mid] || target <= nums[end]) {
start = mid + 1;
} else {
end = mid;
}
} else { // eg. 5,6,1,2,3,4
if (target > nums[mid] && target <= nums[end]) {
start = mid + 1;
} else {
end = mid;
}
}
}
if (start == end && target != nums[start]) return -1;
return start;
}
}