打印二维数组中的某些元素

Question

I'm kinda new to C programming, and I have a certain school assignment I need help solving. Assignment

So, I'm supposed to print out these yellow-marked elements in an array of any given size.

So, here's my code I've come up so far:

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

int main()
{

int i,j,n;

printf("Matrix dimension: ");
scanf("%d",&n);

int matrix[n][n];

srand((unsigned)time(NULL));

for(i=0;i<n;i++)
{
    for(j=0;j<n;j++)
    {
        matrix[i][j]=100+(float)rand()/RAND_MAX*900; //filling out matrix with random integers
    }
}
for(i=0;i<n;i++)
{
    for(j=0;j<n;j++)
    {
        printf("%d\t",matrix[i][j]);    //printing out matrix itself
    }
    printf("\n");
}
printf("\nLeft:\n");    //elements below main diagonal, above secondary diagonal
for(i=1;i<n-1;i++)
{
    printf("\n");
    for(j=0;j<(n-1)/2;j++)
    {
       if((j<i) && (j+i!=n-1))printf("%d\t",matrix[i][j]);
        else printf("-\t");
    }

}
printf("\n\nRight:\n");     //elements above main diagonal, below secondary diagonal
for(i=1;i<n-1;i++)
{
    printf("\n");
    for(j=n-1;j>(n/2);j--)
    {
       if((j>i) &&(i+j!=n-1) )printf("%d\t",matrix[i][j]);
       else printf("-\t");
    }
}

printf("\n\nUp:\n");    //elements above main and secondary diagonal
for(i=0;i<(n-1)/2;i++)
{
    printf("\n");
    for(j=1;j<n-1;j++)
    {
       if((j>i) && (j+i!=n-1 && j+i!=n))printf("%d\t",matrix[i][j]);
       else printf("-\t");
    }
}
printf("\n\nDown:\n");     //elements below main and secondary diagonal
for(i=n-1;i>(n/2);i--)
{
    printf("\n");
    for(j=1;j<n-1;j++)
    {
       if((i>j) &&(i+j!=n-1) )printf("%d\t",matrix[i][j]);
       else printf("-\t");
    }
}
return 0;
}

This code works, but it doesn't work on matrixes whose dimension is equal to 7 or greater. There's always one element extra in those situations. I've realized I can put some extra statements which would solve the problem, but only temporarily. Example:

if((j<i) && (j+i!=n-1 && j+i!=n))

Then it would work on matrixes up to 8x8.

Then I added another statement.

if((j<i) && (j+i!=n-1 && j+i!=n && j+i!=n+1))

And then it would work on matrixes up to 10x10.

So I've noticed that I need to increment j+i statement by 1 every 2 "dimensions".

However, I don't really know how to do that. I tried adding something like

j+i!=n-1+c

where I would set c to zero, and increment in the loop, but it doesnt't work. Also, I would like to print elements as they are in the matrix. So, if I'm printing out right "triangle", I would like if the elements were arranged as they are in the matrix, and not like this: Example of incorrect output

I'd just like to like mirror these numbers, so they're in their spot. So, yeah, that's my problem. I'm sure that there are easier solutions to this, but I'm a C noob, and probably making stuff more complicated than it should be. Anyways, any help is appreciated!

Answer 1

How to

When you need to print your array you need two conditions in order to avoid those that are not yellow. The first condition is obvious.

if(i==j){
 // do not print
}

Second condition is a little less obvious but never the less.

else if(i+j == maxCellSize-1){ //in your case maxCellSize=7
 //do not print
}

Finally after checking those two conditions(preferable combined into one if-statement), you can then print the cell of the array.

else{
    printf("%d", matrix[i][j]);
}

The entire code

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

int main()
{

    int i,j,n;

    printf("Matrix dimension: ");
    scanf("%d",&n);

    int matrix[n][n];

    srand((unsigned)time(NULL));

    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            matrix[i][j]=100+(float)rand()/RAND_MAX*900;  //filling out matrix with random integers
        }
    }
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            if(!(i==j || i+j==n-1)){
             printf("%d\t",matrix[i][j]);    //printing out matrix itself
            }
            else{ printf("X\t");}
        }
        printf("\n");
    }
    printf("\n\n");

    //left
    printf("Left triangle: ");
    for(i=0; i <n; i++){
        for(j=0; j<n/2; j++){
            if(i+j<n && i>j && !(i+j==n-1))
            {
                printf("%d\t",matrix[i][j]); 
            }
        }
    }
    printf("\n");
    //right
    printf("Right triangle: ");
    for(i=1; i <n; i++){
        for(j=n/2; j<n; j++){
            if(!(i==j || i+j==n-1)){
                if(i+j>=n && i<j)
                {
                    printf("%d\t",matrix[i][j]); 
                }

            }
        }
    }

    //top
    printf("\n");
    printf("Top triangle: ");
    for(i=0; i < n/2; i++){
        for(j=1; j<n; j++){
            if(!(i==j || i+j==n-1)){
                if(i+j<n && i<j)
                {
                    printf("%d\t",matrix[i][j]); 
                }

            }
        }
    }

    return 0;
}