feat: add 033

Author: Blankj

README.md

@@ -63,6 +63,7 @@
 |15|[3Sum][015]|Array, Two Pointers|
 |17|[Letter Combinations of a Phone Number][017]|String, Backtracking|
 |19|[Remove Nth Node From End of List][019]|Linked List, Two Pointers|
+|33|[Search in Rotated Sorted Array][033]|Arrays, Binary Search|
 |554|[Brick Wall][554]|Hash Table|
 
 
@@ -122,6 +123,7 @@
 [015]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/015/README.md
 [017]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/017/README.md
 [019]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/019/README.md
+[033]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/033/README.md
 [554]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/554/README.md
 
 [004]: https://github.com/Blankj/awesome-java-leetcode/blob/master/note/004/README.md

note/033/README.md

@@ -0,0 +1,58 @@
+# [Search in Rotated Sorted Array][title]
+
+## Description
+
+Suppose an array sorted in ascending order 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.
+
+**Tags:** Arrays, Binary Search
+
+
+## 思路
+
+题意是让你从一个旋转过后的递增序列中寻找给定值，找到返回索引，找不到返回-1，我们在下面这组数据中寻找规律。
+```
+1 2 4 5 6 7 0
+2 4 5 6 7 0 1
+4 5 6 7 0 1 2
+5 6 7 0 1 2 4
+6 7 0 1 2 4 5
+7 0 1 2 4 5 6
+```
+由于是旋转一次，所以肯定有一半及以上的序列仍然是具有递增性质的，我们观察到如果中间的数比左面的数大的话，那么左半部分序列是递增的，否则右半部分就是递增的，那么我们就可以确定给定值是否在递增序列中，从而决定取舍哪半边。
+
+
+```java
+class Solution {
+ public int search(int[] nums, int target) {
+ int l = 0, r = nums.length - 1, mid;
+ while (l <= r) {
+ mid = l + r >>> 1;
+ if (nums[mid] == target) return mid;
+ else if (nums[mid] >= nums[l]) {
+ if (nums[l] <= target && target < nums[mid]) r = mid - 1;
+ else l = mid + 1;
+ } else {
+ if (nums[mid] < target && target <= nums[r]) l = mid + 1;
+ else r = mid - 1;
+ }
+ }
+ return -1;
+ }
+}
+```
+
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我GitHub上的LeetCode题解：[awesome-java-leetcode][ajl]
+
+
+
+[title]: https://leetcode.com/problems/search-in-rotated-sorted-array
+[ajl]: https://github.com/Blankj/awesome-java-leetcode

src/com/blankj/medium/_033/Solution.java

@@ -0,0 +1,32 @@
+package com.blankj.medium._033;
+
+/**
+ * <pre>
+ * author: Blankj
+ * blog : http://blankj.com
+ * time : 2017/10/16
+ * desc :
+ * </pre>
+ */
+public class Solution {
+ public int search(int[] nums, int target) {
+ int l = 0, r = nums.length - 1, mid;
+ while (l <= r) {
+ mid = l + r >>> 1;
+ if (nums[mid] == target) return mid;
+ else if (nums[mid] >= nums[l]) {
+ if (nums[l] <= target && target < nums[mid]) r = mid - 1;
+ else l = mid + 1;
+ } else {
+ if (nums[mid] < target && target <= nums[r]) l = mid + 1;
+ else r = mid - 1;
+ }
+ }
+ return -1;
+ }
+
+ public static void main(String[] args) {
+ Solution solution = new Solution();
+ System.out.println(solution.search(new int[]{2, 1}, 1));
+ }
+}