問題:
Follow up for “Search in Rotated Sorted Array”:
What if duplicates are allowed?
Would this affect the run-time complexity? How and why?
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
思路一:對於一個有序的,又重複元素的數組旋轉後查找目標值,如果不考慮時間複雜度,可以用數組中的元素依次與目標值進行比較,找到是否存在目標值。
思路二:與前述的沒有重複元素的數組解決方法類似,採用二分查找的遞歸方法,不過由於存在重複元素,無法判斷數組哪側有序,需要兩側都進行判斷再比較。
class Solution {
public boolean search(int[] nums, int target) {
int len = nums.length;
if(len==0){
return false;
}
return dfs(nums,target,0,len-1);
}
public boolean dfs(int []nums,int target,int min,int max){
if(min>max){
return false;
}
int mid = (min+max)/2;
if(nums[mid]==target){
return true;
}
boolean left ;
boolean right;
left = dfs(nums,target,min,mid-1);
right = dfs(nums,target,mid+1,max);
return (left || right);
}
}