Leetcode[33]-Search in Rotated Sorted Array
Link: https://leetcode.com/problems/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.
C++:
方法一:直接for循环求解
class Solution {
public:
int search(vector<int>& nums, int target) {
int n = nums.size();
for(int i = 0; i<n; i++){
if(nums[i] == target) return i;
}
return -1;
}
};
方法二:二分搜索求解
分析:从中点处划分,左右两边一定有一部分是有序的,对于有序的分别做推断。
class Solution {
public:
int search(vector<int>& nums, int target) {
int i = 0, j = nums.size()-1;
while(i<=j){
int mid = (i+j)/2;
if(nums[mid] == target)
return mid;
//if left is sorted
else if(nums[i] <= nums[mid]){
if(nums[i] <= target && target < nums[mid])
j = mid-1;
else
i = mid + 1;
}else {
if(nums[mid] < target && target <= nums[j] )
i = mid +1;
else
j = mid-1;
}
}
return -1;
}
};
posted on 2017-08-13 19:06 gavanwanggw 阅读(207) 评论(0) 编辑 收藏 举报