为什么这段代码会给我超时错误？

Question

I was solving this problem.

Given two sorted arrays arr1[] and arr2[] in non-decreasing order with size n and m. The task is to merge the two sorted arrays into one sorted array (in non-decreasing order).

Note: Expected time complexity is O((n+m) log(n+m)). DO NOT use extra space.
The below code has the time complexity of O(n log m). Still, it gives me a timeout error.

Where am I going wrong?

import java.util.*;
import java.lang.*;
import java.io.*;

class GFG {
    public static void main (String[] args) throws IOException {
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int t = Integer.parseInt(br.readLine());
        
        while(t-- > 0){
            StringTokenizer st = new StringTokenizer(br.readLine());
            int len1 = Integer.parseInt(st.nextToken());
            int len2 = Integer.parseInt(st.nextToken());
            int[] nums1 = new int[len1];
            int[] nums2 = new int[len2];
            
             st = new StringTokenizer(br.readLine());
            
            for(int i = 0; i<len1; i++)
                nums1[i] = Integer.parseInt(st.nextToken());
                
             st = new StringTokenizer(br.readLine());
            
            for(int i = 0; i<len2; i++)
                nums2[i] = Integer.parseInt(st.nextToken());
                
            int temp;
            for(int i =0; i<len1; i++){
                if (nums1[i] > nums2[0]){
                     temp = nums1[i];
                     nums1[i] = nums2[0];
                     nums2[0] = temp;
                     Heapify(nums2,0,len2);
                }
                
            } 
            
            
            for(int i = 0; i<len1; i++)
                System.out.print(nums1[i]+" ");
                
            Arrays.sort(nums2);
            for(int i = 0; i<len2; i++)
                System.out.print(nums2[i]+" ");
            System.out.println();
            
            
        }
        
    }
    
    static void Heapify(int[] nums, int i, int len){
        
        int l = 2 * i+1;
        int r = 2 * i + 2;
        int smallest = i;
        
        if (l < len && nums[l] < nums[i] ){
            smallest = l;
        }
        if (r < len && nums[r] < nums[smallest] ){
            smallest = r;
        }
        if (smallest != i){
            int temp = nums[i];
            nums[i] = nums[smallest];
            nums[smallest] = temp;
            Heapify(nums,smallest,len);
        }
        
    }
    
}

Answer 1

The website has some problems. Submitted same solution for many times.

The timeout was due to there were a lot of read and write operations involved.

You optimised it for read operations using BufferedReader.

I optimised it for write operations using BufferedWriter in the following implementation:

import java.util.*;
import java.lang.*;
import java.io.*;

class GFG {
    public static void main (String[] args) throws IOException {
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int t = Integer.parseInt(br.readLine());
        
        while(t-- > 0){
            StringTokenizer st = new StringTokenizer(br.readLine());
            int len1 = Integer.parseInt(st.nextToken());
            int len2 = Integer.parseInt(st.nextToken());
            int[] nums1 = new int[len1];
            int[] nums2 = new int[len2];
            
             st = new StringTokenizer(br.readLine());
            
            for(int i = 0; i<len1; i++)
                nums1[i] = Integer.parseInt(st.nextToken());
                
             st = new StringTokenizer(br.readLine());
            
            for(int i = 0; i<len2; i++)
                nums2[i] = Integer.parseInt(st.nextToken());
                
            int temp;
            for(int i =0; i<len1; i++){
                if (nums1[i] > nums2[0]){
                     temp = nums1[i];
                     nums1[i] = nums2[0];
                     nums2[0] = temp;
                     Heapify(nums2,0,len2);
                }
                
            } 
            
            BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
            
        
            
            
            for(int i = 0; i<len1; i++)
                log.write(nums1[i]+" ");
                
            Arrays.sort(nums2);
            for(int i = 0; i<len2; i++)
                log.write(nums2[i]+" ");
            log.write("\n");
            
            log.flush();    
            
        }
        
    }
    
    static void Heapify(int[] nums, int i, int len){
        
        int l = 2 * i+1;
        int r = 2 * i + 2;
        int smallest = i;
        
        if (l < len && nums[l] < nums[i] ){
            smallest = l;
        }
        if (r < len && nums[r] < nums[smallest] ){
            smallest = r;
        }
        if (smallest != i){
            int temp = nums[i];
            nums[i] = nums[smallest];
            nums[smallest] = temp;
            Heapify(nums,smallest,len);
        }
        
    }
    
}

The Geeks for Geeks verdict is Accepted for the above code:

PS: Try to submit this same solution for multiple times. You will get correct answer as verdict.