leetcode——33——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 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.

class Solution {
public:
int search(vector<int>& nums, int target) {
// 初始问题
int l = 0, r = nums.size() - 1;
// 不断重复来缩小问题规模
while (l < r) {
// 取中点，分情况讨论
int m = (l + r) / 2;
// 情况0
if (target == nums[m]) return m;
// 情况1
if (nums[l] < nums[r]) {
if (target > nums[m]) l = m + 1;
if (target < nums[m]) r = m - 1;
}
else {
// 情况2.1
if (nums[m] >= nums[l]) {
if (target > nums[m] || target < nums[l]) {
l = m + 1;
}
else {
r = m - 1;
}
}
// 情况2.2
else {
if (target < nums[m] || target > nums[r]) {
r = m - 1;
}
else {
l = m + 1;
}
}
}
}
// 计算答案
if (l == r && nums[l] == target) return l;
return -1;
}
};