153. Find Minimum in Rotated Sorted Array
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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).
Find the minimum element.
You may assume no duplicate exists in the array.
第二刷,还是不太优雅,代码如下:
public int findMin(int[] nums) { int begin = 0; int end = nums.length-1; if (nums[end] > nums[begin]) return nums[begin]; while(begin < end){ int p = (begin + end) >>> 1; if (nums[begin] >= nums[0]) { if (nums[p] > nums[begin]) begin = p; else if (nums[p] < nums[begin]) end = p; else return Math.min(nums[begin], nums[end]); } else { if (nums[p] > nums[begin]) end = p; else if (nums[p] < nums[begin]) begin = p; else return nums[begin]; } } return nums[end]; }
以题目的input为例,是这样想的,先比较nums[begin]与nums[0]
如果nums[begin]<nums[0] 那么nums[0]到nums[begin]这段位于4567
nums[begin]<nums[0] 这段位于012
然后用nums[p]与nums[begin]的关系确定后续的搜索空间是向左移,还是向右移动
1.区间位于4567,如果nums[p] > nums[begin],那么后续的搜索应该向右移
2.区间位于012,nums[p] > nums[begin],那么后续的搜索空间应该是在左半段
但实际上 第二种情况是不存在的
如果nums[begin]<nums[0] 也就是nums[begin]到nums[end]位于012内 是sorted array 那么就不需要在搜索了 返回nums[bein]就可以了
只有nums[begin]>nums[0] 也就是nums[begin]到nums[end]不确定是否是sorted array时 才需要继续搜索
所以rotated问题的关键在于 找到sorted array 使用binary search
以下是solution
int findMin(vector<int> &num) { int start=0,end=num.size()-1; while (start<end) { if (num[start]<num[end]) return num[start]; int mid = (start+end)/2; if (num[mid]>=num[start]) { start = mid+1; } else { end = mid; } } return num[start];}
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- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array **
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
- 153. Find Minimum in Rotated Sorted Array
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