自己寫的，雖然過了，但是其實是有問題的

class Solution {
    public int[] searchRange(int[] nums, int target) {
        
        if(nums==null||nums.length==0)return new int[]{-1,-1};
        int n=nums.length;
        int low=0;
        int hi=n-1;
       
        
        int leftplace=-1;
        int rightplace=-1;
        
        if(nums[n-1]==target)rightplace=n-1;
        if(nums[0]==target)leftplace=0;
        
        
        while(low<=hi){
            int mid=(low+hi)/2;
        
            if(low==hi){
                if(nums[low]<=target-1){
                    leftplace=hi+1;
                     if(leftplace<n&&nums[leftplace]!=target) leftplace=-1;
                   
                    break;
                }
                if(nums[low]==target){
                     
                    leftplace=low;
                    
                    break;
                }
            }
            if(nums[mid]>target-1){
                hi=mid-1;
            }
            else if(nums[mid]<target-1){
                low=mid+1;
            }
            else{
                leftplace=mid+1;
                
                break;
            }
        }
        
     
       
        
        
        while(leftplace>=0&&leftplace<n&&nums[leftplace]<target){
            leftplace++;
           
        }
        if(leftplace>=0&&leftplace<n&&nums[leftplace]!=target) leftplace=-1;
        
      
        if(leftplace==n)leftplace=-1;
        
       
        
        low=0;
        hi=n-1;
        while(low<=hi){
            int mid=(low+hi)/2;
            
            if(low==hi){
                if(nums[hi]>=target+1){
                    rightplace=hi-1;
                    if(rightplace>=0&&nums[rightplace]!=target) rightplace=-1;
                    break;
                }
                if(nums[low]==target){
                    rightplace=low;
                    break;
                }
            }
            if(nums[mid]>target+1){
                hi=mid-1;
            }
            else if(nums[mid]<target+1){
                low=mid+1;
            }
            else{
                rightplace=mid-1;
                break;
            }
        }
        
        
        while(rightplace<n&&rightplace>=0&&nums[rightplace]>target){
            rightplace--;
        }
        if(rightplace>=0&&rightplace<n&&nums[rightplace]!=target) rightplace=-1;
       
        
        
        return new int[]{leftplace,rightplace};
    }
}
 

Solution 1:找最左邊的和最右的後一個

當low==hi的時候退出，low每次除去比target小的部分，hi每次都在比target稍大的位子

class Solution {
    // returns leftmost (or rightmost) index at which `target` should be
    // inserted in sorted array `nums` via binary search.
    private int extremeInsertionIndex(int[] nums, int target, boolean left) {
        int lo = 0;
        int hi = nums.length;

        while (lo < hi) {
            int mid = (lo + hi) / 2;
            if (nums[mid] > target || (left && target == nums[mid])) {
                hi = mid;
            }
            else {
                lo = mid+1;
            }
        }

        return lo;
    }

    public int[] searchRange(int[] nums, int target) {
        int[] targetRange = {-1, -1};

        int leftIdx = extremeInsertionIndex(nums, target, true);

        // assert that `leftIdx` is within the array bounds and that `target`
        // is actually in `nums`.
        if (leftIdx == nums.length || nums[leftIdx] != target) {
            return targetRange;
        }

        targetRange[0] = leftIdx;
        targetRange[1] = extremeInsertionIndex(nums, target, false)-1;

        return targetRange;
    }
}