[LeetCode]540. Single Element in a Sorted Array
2017-08-03 22:55
423 查看
[LeetCode]540. Single Element in a Sorted Array
题目描述
思路
开始的想法,直接用位操作,异或即可得到结果,但是需要o(n)时间题目要求是o(logn),并且给出数组是有序的,因此可以使用二分的方法来做
对于整个数组,取mid,如果mid为偶数,判断mid值是否和mid+1相等,如果相等,则说明只出现一次的数在右边,需要向右边找,原因,mid为偶数时,分割成的两段数组长度均为偶数,如果mid和mid+1相等,那么除去这个mid+1的值,只剩奇数个数,要找的数必然在这奇数个数中,同理可以推断mid为奇数时候的情况
代码
#include <iostream> #include <vector> using namespace std; class Solution { public: int singleNonDuplicate(vector<int> & nums) { /* int res = 0; for (int num : nums) res ^= num; return res; */ int start = 0, end = nums.size() - 1; while (start < end) { int mid = (start + end) / 2; if (mid % 2 == 0) { if (mid + 1 < nums.size() && nums[mid] == nums[mid + 1]) start = mid + 2; else if (mid - 1 >= 0 && nums[mid - 1] == nums[mid]) end = mid - 2; else return nums[mid]; } else { if (mid + 1 < nums.size() && nums[mid] == nums[mid + 1]) end = mid - 1; else if (mid - 1 >= 0 && nums[mid - 1] == nums[mid]) start = mid + 1; } } return nums[start]; } }; int main() { Solution s; vector<int> nums = { -1, -1, 3, 3, 5, 7, 7, 9, 9 }; cout << s.singleNonDuplicate(nums) << endl; system("pause"); return 0; }
相关文章推荐
- leetcode 540. Single Element in a Sorted Array
- leetcode 540. Single Element in a Sorted Array
- (Java) LeetCode 540. Single Element in a Sorted Array —— 有序数组中的单一元素
- LeetCode 540. Single Element in a Sorted Array
- {LeetCode} 540. Single Element in a Sorted Array
- LeetCode 540. Single Element in a Sorted Array (Medium)
- python--leetcode540. Single Element in a Sorted Array
- LeetCode | 540. Single Element in a Sorted Array
- [LeetCode]540. Single Element in a Sorted Array
- LeetCode 540. Single Element in a Sorted Array
- LeetCode - 540. Single Element in a Sorted Array
- leetcode 540. Single Element in a Sorted Array 题解
- [LeetCode] 540. Single Element in a Sorted Array
- 【LeetCode】540. Single Element in a Sorted Array
- LeetCode 540. Single Element in a Sorted Array
- leetcode 540. Single Element in a Sorted Array
- 【LeetCode】540. Single Element in a Sorted Array 解题报告
- [Leetcode] 540. Single Element in a Sorted Array 解题报告
- 540. Single Element in a Sorted Array
- LeetCode (Single Element in a Sorted Array)