static int count=0; static void printOutput(ArrayList arr){ count++; int sum=0; for(int i=0;i arr,int i,int n) { if(n==0){ printOutput(arr); } for(int į = i; j <= n; j++) { arr.add(j); findways(arr, i, n: n - j); arr.remove( index: arr.size() - 1); } } public static void main(String[] args)throws IOException { BufferedReader br=new BufferedReader (new InputStreamReader(System.in) int n=Integer.parseInt(br.readLine()); ArrayList arr = new ArrayList<>(); findways(arr, : 1,n); System.out.println("total="+(count-1));

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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Attached is a programming question and its Java solution.

My question regarding the recursion part:

     1. "arr.add(j)" but then "arr.remove(arr.size() - 1)" follows soon after, and I think nothing should be printed. How does the program still print out permutations? Is it because the recursive method call only recurse all instructions from the start of the recursion method to that line? Otherwise, say the input is "5", how does "5=1+1+1+1+1" get printed?

     2. Does the recursion stop when "j<=n" evaluates false because of "for(int j = i; j <= n; j++)"? Otherwise, which line of code tells the recursion to stop?

Ryuk the shinigami wants to find out the different ways to add up to N apples! For example, if you have 3 apples, the
possible ways are:
3=1+1+1
3=1+2
total=2
Ryuk wants you, to output the solution in the above format given the number of apples, N.
Note: The sequence which you output the solution does not matter, meaning:
3=1+1+1
3=1+2
and
3=1+2
3=1+1+1
are both accepted.
Transcribed Image Text:Ryuk the shinigami wants to find out the different ways to add up to N apples! For example, if you have 3 apples, the possible ways are: 3=1+1+1 3=1+2 total=2 Ryuk wants you, to output the solution in the above format given the number of apples, N. Note: The sequence which you output the solution does not matter, meaning: 3=1+1+1 3=1+2 and 3=1+2 3=1+1+1 are both accepted.
static int count=0;
static void printOutput(ArrayList<Integer> arr){
count++;
int sum=0;
for (int i=0;i<arr.size();i++){
sum+=arr.get (i);
}
if (arr.size() != 1){
System.out.print(sum+"=");
for(int i=0;i<arr.size()-1;i++){
System.out.print(arr.get(i)+"+");
}
System.out.println(arr.get(arr.size()-1));|
}
}
static void findWays (ArrayList<Integer> arr,int i,int n)
{
if(n==0){
printOutput (arr);
}
for(int i
i; j <= n; j++)
{
arr.add(j);
findways (arr, ji, n: n - j);
arr.remove( index: arr.size() - 1);
}
}
public static void main(String[] args)throws IOException {
BufferedReader br=new BufferedReader(new InputStreamReader (System.in));
int n=Integer.parseInt(br.readLine());
ArrayList<Integer> arr = new ArrayList<>();
findways (arr, : 1,n);
System.out.println("total="+(count-1));
Transcribed Image Text:static int count=0; static void printOutput(ArrayList<Integer> arr){ count++; int sum=0; for (int i=0;i<arr.size();i++){ sum+=arr.get (i); } if (arr.size() != 1){ System.out.print(sum+"="); for(int i=0;i<arr.size()-1;i++){ System.out.print(arr.get(i)+"+"); } System.out.println(arr.get(arr.size()-1));| } } static void findWays (ArrayList<Integer> arr,int i,int n) { if(n==0){ printOutput (arr); } for(int i i; j <= n; j++) { arr.add(j); findways (arr, ji, n: n - j); arr.remove( index: arr.size() - 1); } } public static void main(String[] args)throws IOException { BufferedReader br=new BufferedReader(new InputStreamReader (System.in)); int n=Integer.parseInt(br.readLine()); ArrayList<Integer> arr = new ArrayList<>(); findways (arr, : 1,n); System.out.println("total="+(count-1));
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