[Ctrip 2018 School Recruitment] Non-zero elements in the array are stably placed in the front of the array, and zero elements are placed in the back of the array

Topic description:

Given an array, without applying for a new array , put non-zero elements in the array stably at the front of the array, and zero elements in the back of the array. Stability means that the relative positions of non-zero elements do not change. The topic is very simple, let's talk about the blog.

Problem solving plan:

The first method is similar to the method such as insertion sort. It traverses the array and moves it forward if it encounters a non-zero element until the previous element is not 0 or to the top of the array.

The second method, with fewer operations, uses an auxiliary subscript starting from zero, traverses the array, and if a non-zero element is encountered, it is assigned to the position of the auxiliary subscript, and then the auxiliary subscript is added.

Code:

import java.util.Scanner;

public class FirstQues {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		
		int num = in.nextInt();
		int[]  primaryArr = new int[num];
		for(int i=0; i<num; i++){
			primaryArr[i] = in.nextInt();
		}
	
//		settleArr1(primaryArr);
		settleArr2(primaryArr);

		for(int q=0; q<primaryArr.length; q++){
			System.out.print(primaryArr[q] + " ");
		}
	}
	
	public static void settleArr1(int[] primaryArr){
		boolean flag=false;
		for(int x=1; x<primaryArr.length; x++){
			// if the value of x at this position is not 0
			if(primaryArr[x]!=0){
				// and there is 0 in front of it, move the current position forward until it is not 0 or to the top of the array
				for(int j= x-1; primaryArr[j]==0 && j>=0; j--){
					primaryArr[j] = primaryArr[j+1];
					// The current position moves forward, then this position should be filled with 0
					primaryArr[j+1] = 0;
					// If j is 0, it cannot be subtracted, otherwise the array will be out of bounds
					if(j==0) break;
				}
			}
		}
	}

	public static void settleArr2(int[] primaryArr){
		int index =0;
		for(int i =0 ; i<primaryArr.length; i++){
			if(primaryArr[i]!=0){
				primaryArr[index]= primaryArr[i];
				if(index != i)
					primaryArr[i] = 0;
				index++;
			}
		}
	}
}

Test Results: