The reverse of all numbers on the 5th column on matrix [closed] - c

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I have a C problem where I need to reverse all the numbers on the 5th column of a 2x5 matrix.
So if I have
1 2 3 4 89
3 8 6 8 91
This will become
1 2 3 4 98
3 8 6 8 19
The code I've written so far is:
#include <stdio.h>
void inverse() {
int reversedNumber = 0, remainder, mat[10][10], i, j;
for (i = 0; i < 2; i++)
for (j = 0; j < 5; j++) {
while (mat[i][j] != 0) {
remainder = mat[i][j] % 10;
reversedNumber = reversedNumber * 10 + remainder;
mat[i][j] /= 10;
}
}
printf("Reversed Number = %d", reversedNumber);
}
void main()
{
int mat[10][10], i, j;
printf("Enter your matrix\n");
for (i = 0; i < 2; i++)
for (j = 0; j < 5; j++) {
scanf("%d", &mat[i][j]);
}
printf("\nHere is your matrix:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 5; j++) {
printf("%d ", mat[i][j]);
}
printf("\n");
}
inverse(mat[1][5]);
}
After running this I get a ridiculously large number! What should I modify?

Answer 1

There are number of things that can be improved in the code.
First of all you have to set reversedNumber zero inside the innermost loop, this is the reason you get large numbers.
You pass an argument to the function, but the definition is incorrect for the same.
Also, you have stated that you only need to reverse the 5th column, better make call to a function that reverses a single number.
#include<stdio.h>
int inverse(int num) {
int reversednum = 0;
while(num){
reversednum = reversednum*10 + num%10;
num /= 10;
}
return reversednum;
}
void main(){
int mat[10][10],i,j;
printf("Enter your matrix\n");
for(i=0;i<2;i++)
for(j=0;j<5;j++){
scanf("%d",&mat[i][j]);
}
printf("\nHere is your matrix:\n");
for(i=0;i<2;i++){
for(j=0;j<5;j++){
printf("%d ",mat[i][j]);
if(j == 4) mat[i][j] = inverse(mat[i][j]);
}
printf("\n");
}
}

Answer 2

mistakes in your program:
-your function doesnt expect anything i.e empty parameter but you are sending matrix as parameter.
do not unnecessarily use matrix of size [10][10] when your matrix of 2*5
send 'mat' as parameter(i.e address of your matrix) to function inverse
#include <stdio.h>
int main() {
//code
int mat[10][10], i, j;
printf("Enter your matrix\n");
for (i = 0; i < 2; i++)
for (j = 0; j < 5; j++) {
scanf("%d", &mat[i][j]);
}
printf("\nHere is your matrix:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 5; j++) {
if(j==4) //only for 5th column
{
// int temp=mat[i][j]; // can use temporary variable instead of changing actual value matrix (better option)
int remainder, reverse =0;
while(mat[i][j]>0)
{
remainder=mat[i][j]%10;
reverse=reverse*10 + remainder;
mat[i][j]=mat[i][j]/10;
}
mat[i][j]=reverse;
}
printf("%d ", mat[i][j]);
}
printf("\n");
}
return 0;
}
Edited: modified code from the question
#include <stdio.h>
void inverse(int mat1[2][5]) {
int i, j;
for (i = 0; i < 2; i++){
int j=4;
int reversedNumber = 0, remainder=0;
while (mat1[i][j] > 0) {
remainder = mat1[i][j] % 10;
reversedNumber = reversedNumber * 10 + remainder;
mat1[i][j] /= 10;
}
printf("Reversed Number = %d\n",reversedNumber);
}
}
void main()
{
int mat[2][5], i, j;
printf("Enter your matrix\n");
for (i = 0; i < 2; i++)
for (j = 0; j < 5; j++) {
scanf("%d", &mat[i][j]);
}
printf("\nHere is your matrix:\n");
for (i = 0; i < 2; i++) {
for (j = 0; j < 5; j++) {
printf("%d ", mat[i][j]);
}
printf("\n");
}
inverse(mat);
}
hope this helps.

Answer 3

You have to pass the matrix to the inverse function so that the matrix (mat) can be modified. If you declare a separate mat array inside inverse then that's a different scope. You also have to figure out how many digits there are in the number. You can use <math.h> functions, or the example below uses basic calculations.
void inverse(int mat[2][5])
{
for(int i = 0; i < 2; i++)
for(int j = 0; j < 5; j++)
{
int n = mat[i][j];
int digits = 0;
while(n > 0)
{
digits++;
n /= 10;
}
n = mat[i][j];
int rev = 0;
while(digits > 0)
{
int x = n % 10;
for(int c = 0; c < digits - 1; c++)
x *= 10;
rev += x;
n /= 10;
digits--;
}
mat[i][j] = rev;
}
}
int main(void)
{
int mat[2][5] = {
1, 2, 3, 4, 89,
3, 8, 6, 8, 91 };
inverse(mat);
for(int i = 0; i < 2; i++)
{
for(int j = 0; j < 5; j++)
printf("%d ", mat[i][j]);
printf("\n");
}
return 0;
}