DFS using Adjacency Matrix

#include <stdio.h>
#include <stdlib.h>
char **a;
int *visited, n;
void dfs(int x){
    int y;
    visited[x] = 1;
    printf(" %c ", 'A' + x); //index converted to char by adding A
    for(y = 0; y < n; y++)
        if(!visited[y] && a[x][y] == 'Y')
            dfs(y);
}
void buildAdjacentMatrix(){
    int i, j, choice;
    printf("\n Enter number of vertices:");
    scanf("%d",&n);
    a =(char**) malloc(sizeof(char*) * n);
    for(i = 0; i < n; i++) a[i] = (char*) malloc(n * sizeof(char)); //alternate to char a[n][n]
    visited = (int*) malloc(sizeof(int)*n); //alternate to int visited[n]
    for(i = 0; i < n; i++) visited[i] = 0;
    for(i = 0; i < n; i++)
        for(j = 0; j <= i; j++){
            printf("Are vertices %c and %c linked?: ", 'A' + i, 'A' + j);
            scanf("%d", &choice);
            if(choice == 1) a[i][j] = a[j][i] = 'Y';
            else a[i][j] = a[j][i] = 'N';
        }
    printf("The graph is:-\n");
    for(i = 0; i < n; i++) printf("\t%c", 'A'+i);
    printf("\n\n\n");
    for(i = 0; i < n; i++){
        printf("%c", 'A'+i);
        for(j = 0; j < n; j++) printf("\t%c", a[i][j]);
        printf("\n\n\n");
    }
}
int main(){
    char ch;
    buildAdjacentMatrix();
    printf("Start from which vertex?: ");
    fflush(stdin); //Clears input stream
    ch = getchar(); // char input from user
    if(ch >= 'A' && ch <= ('A' + n-1)) dfs(ch-'A'); //DFS starts from user inputted alphabet.
    else printf("Error.");
    return 0;
 }