Follow up for "Search in Rotated Sorted Array":
What if duplicates are allowed?
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.
» Solve this problem[解题思路]
确实有影响。比如,上一题(http://fisherlei.blogspot.com/2013/01/leetcode-search-in-rotated-sorted-array.html)的程序中默认如果A[m]>=A[l],那么[l,m]为递增序列的假设就不能成立了,比如如下数据
[1,3,1,1,1]
所以,要是想增强该假设,有两个选择
1. 对于每一个递增序列,遍历之,确认。
2. 找到pivot点,然后确定对应序列搜索。
不写代码了。
Update: 3/18/2013. add the implementation
重新想了一下,其实不需要这么复杂。如果A[m]>=A[l]不能确定递增,那就把它拆分成两个条件
1. A[m]>A[l] 递增
2. A[m] ==A[l] 确定不了,那就l++,往下看一步即可。
实现如下
1: bool search(int A[], int n, int target) { 2: int start = 0; 3: int end = n-1; 4: while(start <= end) 5: { 6: int mid = (start+end)/2; 7: if(A[mid] == target) return true; 8: if(A[start] < A[mid]) 9: { 10: if(target>=A[start] && target<A[mid]) 11: end = mid-1; 12: else 13: start = mid+1; 14: } 15: else if(A[start] > A[mid]) 16: { 17: if(target>A[mid] && target<=A[end]) 18: start = mid+1; 19: else 20: end = mid-1; 21: } 22:
else //skip duplicate one, A[start] == A[mid] 23: start++;
24: } 25: return false; 26: }
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