Find First and Last Position of Element in Sorted Array (LeetCode)
Given an array of integers nums
sorted in ascending order, find the starting and ending position of a given target
value.
If target
is not found in the array, return [-1, -1]
.
You must write an algorithm with O(log n)
runtime complexity.
Examples:
Input: nums = [5,7,7,8,8,10], target = 8 Output: [3,4]
Input: nums = [], target = 0 Output: [-1,-1]
Solution (Java):
class Solution {
public int[] searchRange(int[] nums, int target) {
int[] ans={-1,-1};
int start=searchPosition(nums,target,true);
int end=searchPosition(nums,target,false);
ans[0]=start;
ans[1]=end;
return ans;
}
int searchPosition(int[]nums, int target, boolean WantStartElement){
int start=0, end=nums.length-1,ans=-1;
while(start<=end){
int mid=start+(end-start)/2;
if(target<nums[mid])
end=mid-1;
else if(target>nums[mid])
start=mid+1;
else{
ans=mid;
if(WantStartElement)
end=mid-1;
else
start= mid+1;
}
}
return ans;
}
}
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