Example: Upper Triangular Matrix example in C using for loop

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// Upper Triangular Matrix example in C using for loop
#include <stdio.h>

int main() {
    int size, flag = 0, i, j;

    printf("Enter the size of the matrix: ");
    scanf("%d", &size);

    int matrix[size][size];

    printf("\nEnter the matrix's elements:\n");
    for(i = 0; i < size; i++) {
        for(j = 0; j < size; j++)
            scanf("%d", &matrix[i][j]);
        printf("\n");
    }

    for (i = 1; i < size; i++) {
        for (j = 0; j < i; j++) {
            if (matrix[i][j] != 0)
                flag = 0;
            else
                flag = 1;
        }
    }
  
    if (flag == 1)
        printf("This is the Upper Triangular Matrix.\n");
    else
        printf("This not an Upper Triangular Matrix!\n");
    
    return 0;
}