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【LeetCode】Search in Rotated Sorted Array II (2 solutions)

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.

 

解法一:顺序查找

class Solution {public:    bool search(int A[], int n, int target) {        for(int i = 0; i < n; i ++)        {            if(A[i] == target)                return true;        }        return false;    }};

 

解法二:二分查找

关键点在于,如果mid元素与low或者high元素相同,则删除一个low或者high

class Solution {public:    bool search(int A[], int n, int target) {        int low = 0;        int high = n-1;        while (low <= high)        {            int mid = (low+high)/2;            if(A[mid] == target)                 return true;            if (A[low] < A[mid])            {                if(A[low] <= target && target < A[mid])                //binary search in sorted A[low~mid-1]                    high = mid - 1;                else                //subproblem from low to high                    low = mid + 1;            }            else if(A[mid] < A[high])            {                if(A[mid] < target && target <= A[high])                //binary search in sorted A[mid+1~high]                    low = mid + 1;                else                //subproblem from low to mid-1                    high = mid - 1;            }            else if(A[low] == A[mid])                low += 1;    //A[low]==A[mid] is not the target, so remove it            else if(A[mid] == A[high])                high -= 1;  //A[high]==A[mid] is not the target, so remove it        }        return false;    }};

【LeetCode】Search in Rotated Sorted Array II (2 solutions)