Question

C programmning help

Vector permutation

can anyone explain whats happening in the bold statements ? im not too sure about it . thank you

//z5285994
#include <stdio.h>
#include <math.h>
int main(void){
int vector_length, v1[1000], permutation[1000];
  
printf("Enter vector length: ");
scanf("%d", &vector_length);
int i;
  
printf("Enter vector: ");
for (i=1;i<= vector_length; i++){
scanf("%d",&v1[i]);
}
  
printf("Enter permutation: ");
for (i = 1; i <= vector_length; i++){
scanf("%d", &permutation[i]);
}
  
for (i = 1;i <= vector_length; i++){
printf("%d ", v1[permutation[i]+1]);
  
}
printf("\n");
  

return 0;
}

Answer 1

#include <stdio.h>//includes standard libraries.
#include <math.h>//includes math libraries.
int main(void) //main function which has void as argument.. ie it takes nothing or void as argument.

{
int vector_length, v1[1000], permutation[1000]; // vector_length is a variable of integer type and v1[1000] and permutation[1000] are array of size 1000 of integer type.
  
printf("Enter vector length: ");
scanf("%d", &vector_length); //this statement stores the length of the vector.. example:vector length is 2.
int i;// i is a variable of integer type.
  
printf("Enter vector: ");

for (i=1;i<= vector_length; i++) //number of iteration of this for loop is less than or equal to the lenght of vector.. by the example: iteration is 2 times.

{
scanf("%d",&v1[i]);  //inside the for loop numbers of elements are stored into the array v1. That is:v1[1] stores a given number in 1st iteration then v1[2] stores another number in the second iteration and so on depending on the number of iteration(in this case vector lenght).
}
  
printf("Enter permutation: ");

for (i = 1; i <= vector_length; i++) //this for loop is same as above for loop and repeats itself if 'i' is less than or equal to the vector length. ie: iterates 2 times

{
scanf("%d", &permutation[i]);// it stores number of elements in the permutation array. ie: permutation[1] stores a given number in its 1st iteration and permutation[2] stores another number in other iteration.
}

for (i = 1;i <= vector_length; i++) //this for loop prints the value for number of iterations which is less than or equal to the vector length.

{

printf("%d ", v1[permutation[i]+1]);

// prints the array v1[permutation[i]+1] =>v1[permutation[1]+1] =>v1[permutation[2]] => v1[given number] if there is any number stored at the index of v1[permutation[i]+1] then it may print the value or else 0 or garbage value(by the example if vector length is 2).
//this process repeats for no of iterations which is less than or equal to vector length.
  
}
printf("\n");//\n is an escape sequence used to print on next line
  

return 0;
}

//hope it helps