String; replace diagonal by minimum

String

A string is a sequence of characters stored in a character array and ended by the null character '\0'. It is declared as char name[20]; and can be initialised as char name[] = "Nepal"; (6 bytes including '\0'). Strings are read with scanf("%s"), gets() or fgets(), printed with %s, and handled with <string.h> functions such as strlen, strcpy, strcmp and strcat.

Program

A pointer p is set to the first element of the matrix. A 2D array is stored row by row, so element a[i][j] is *(p + i*3 + j). The program finds the minimum with the pointer, puts it on the diagonal positions (i = j), and prints the matrix using the pointer.

#include <stdio.h>

int main(void)
{
    int a[3][3], *p = &a[0][0], min;

    printf("Enter 9 integers: ");
    for (int i = 0; i < 9; i++)
        scanf("%d", p + i);              /* p + i is the address of element i */

    min = *p;
    for (int i = 1; i < 9; i++)
        if (*(p + i) < min)
            min = *(p + i);

    for (int i = 0; i < 3; i++)
        *(p + i * 3 + i) = min;          /* a[i][i] = min */

    printf("Minimum = %d\nMatrix after replacing the diagonal:\n", min);
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++)
            printf("%4d", *(p + i * 3 + j));
        printf("\n");
    }
    return 0;
}

Sample run (matrix 7 2 9 / 4 8 6 / 5 3 1)

Input: 7 2 9 4 8 6 5 3 1

Enter 9 integers: Minimum = 1
Matrix after replacing the diagonal:
   1   2   9
   4   1   6
   5   3   1