Leetcode | Search in Rotated Sorted Array I & II
2014-05-18 19:36
661 查看
Search in Rotated Sorted Array I
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.
Have you been asked this question in an interview?
二分查找。
1. 如果A[mid]>A[l],也就是A[l...mid]是递增序。如果target>=A[l]&&target<A[mid],那么target只可能在[l...mid-1]这个区间上,否则在[mid+1...h]这个区间。
2. 如果A[mid]<=A[l],那么A[mid...h]是递增序。如果target>A[mid] && target<=A[h],那么target只可能在[mid+1...h]这个区间,否则在[l...mid-1]这个区间。
class Solution { public: int search(int A[], int n, int target) { if (n == 0) return -1; int l = 0, h = n - 1, mid; while (l <= h) { mid = (l + h) / 2; if (A[mid] == target) return mid; if (A[mid] >= A[l]) { if (target >= A[l] && target < A[mid]) { h = mid - 1; } else { l = mid + 1; } } else { if (target > A[mid] && target <= A[h]) { l = mid + 1; } else { h = mid - 1; } } } return -1; } };
Search in Rotated Sorted Array II
Follow up for "Search in Rotated Sorted Array":What if duplicates are allowed?
Would this affect the run-time complexity? How and why?
Write a function to determine if a given target is in the array.
有了重复数。那么前面的情况,只对应于A[mid]>A[l]和A[mid]<A[l]是成立的。对于A[mid]==A[l],我们无法确定该数是在左区间还是右区间,反正一定不会是在A[l]上,所以l++。
最坏情况就是整个数组都是同一个数,target不在数组中,这样每次都只能l++,算法复杂度是O(n)。
class Solution { public: bool search(int A[], int n, int target) { if (n == 0) return false; int l = 0, h = n - 1, mid; while (l <= h) { mid = (l + h) / 2; if (A[mid] == target) return true; if (A[mid] == A[l]) { l++; } else if (A[mid] > A[l]) { if (target >= A[l] && target < A[mid]) { h = mid - 1; } else { l = mid + 1; } } else { if (target > A[mid] && target <= A[h]) { l = mid + 1; } else { h = mid - 1; } } } return false; } };
相关文章推荐
- [LeetCode]Search in Rotated Sorted Array I&II
- [LeetCode]Search in Rotated Sorted Array I && II
- 【LeetCode从零单刷】Search in Rotated Sorted Array I & II
- [LeetCode] Search in Rotated Sorted Array I (33) && II (81) 解题思路
- Leetcode-Search in Rotated Sorted Array&&Search in Rotated Sorted ArrayII
- LeetCode 33. Search in Rotated Sorted Array && 81. Search in Rotated Sorted Array II
- Leetcode: Search in Rotated Sorted Array & II
- leetcode题解-33. Search in Rotated Sorted Array && 81. Search in Rotated Sorted Array II
- Leetcode Search in Rotated Sorted Array I && II
- !leetcode[33&81]:Search in Rotated Sorted Array[I & II]
- 【LeetCode】Search in Rotated Sorted Array && Search in Rotated Sorted Array II
- leetcode -- Search in Rotated Sorted Array I &II 重点可以考
- leetcode - Search in Rotated Sorted Array I & II
- Leetcode: Search in Rotated Sorted Array II
- [LeetCode] Search in Rotated Sorted Array II
- leetcode 98: Search in Rotated Sorted Array II
- [LeetCode] Search in Rotated Sorted Array II
- Search in Rotated Sorted Array II [LeetCode]
- LeetCode Online Judge 题目C# 练习 - Search in Rotated Sorted Array II
- LeetCode: Search in Rotated Sorted Array II