Li Kou brush question diary /day8/7.1

Novice Village

Bubble sort ：

Realize the orderly arrangement of elements in the array according to the numerical size （ Ascending , Descending ）

Realization thought ：（ Take descending as an example ）

1. Compare the first data with the second data , If the first data is smaller than the second data , Exchange the two data locations

2. The pointer points from the first data to the second data , The second data is compared with the third data , If the second data is smaller than the third data , Exchange the two data locations

3. By analogy , Complete the first round of sorting , After the first round of sorting , The largest element is moved to the far right

4. Repeat the above process , After each row , The number of comparisons is less than once

Coding ideas ： It takes two cycles , Layer 1 cycle i Indicates the number of rounds of sorting , The second cycle j Indicates the number of comparisons

For example, a simpler bubble sort , Put the first number and the following number Compare sizes one by one , If it is less than , Then swap positions , Greater than, it will not move . here , The first number is the maximum number in the array . Then compare the second number with the following numbers one by one , And so on .

public class Test { 
    public static void main(String[] args) { 
        int [] array = {12,3,1254,235,435,236,25,34,23}; 
        int temp; 
        for (int i = 0; i < array.length; i++) { 
            for (int j = i+1; j < array.length; j++) { 
                if (array[i] < array[j]) { 
                       temp = array[i]; 
                       array[i] = array[j]; 
                       array[j] = temp; //  Two numbers exchange positions  
                    } 
                } 
             }
            for (int i = 0; i < array.length; i++) { 
                    System.out.print(array[i]+"  "); 
            } 
        } 
}

  Example ：

 

class Solution {
    public int findKthLargest(int[] nums, int k) {
        for(int i=0;i<nums.length;i++){
            int temp;
            for(int j=i+1;j<nums.length;j++){
                if(nums[i]<nums[j]){
                    temp=nums[i];
                    nums[i]=nums[j];
                    nums[j]=temp;
                }
            }
        }
        int ans=nums[k-1];
        return ans;
    }
}