// This program will construct and display an n*n identity matrix.
 
#include <stddef.h>
#include <stdio.h>
 
int main(void)
{
    size_t n=0;
 
    printf("Please input `n': \n");
    scanf("%zu", &n);
 
    int matrix[n][n];
 
    for (size_t i=0; i < n; ++i)
        for (size_t j=0; j < n; ++j)
            if (i == j)
                matrix[i][j] = 1;
            else
                matrix[i][j] = 0;
 
    for (size_t i=0; i < n; ++i)
    {
        for (size_t j=0; j < n; ++j)
            printf("%d ", matrix[i][j]);
 
        printf("\n");
    }
}

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