#include <stdio.h>
#include <string.h>

int max(int values[], int N) {
    int i, max = values[0];
    for(i=1; i<N; i++) {
        if (max < values[i]) max = values[i];
    }
    return max;
}

void histogram(char * result,int * values, int numValues) {
    int i, j, h;
    h = max(values,numValues);
    strcpy(result,"");
    for (i=0; i<(h+2); i++) {
        if (i==0 || i==h+1) {
            for (j=0; j<(numValues+2); j++){
                strcat(result,"*");
            }
            strcat(result,"\n");
        }
        else
            for (j=0; j<(numValues+3); j++){
                if (j==0 || j==numValues+1) strcat(result,"*");
                else if (j==numValues+2)  strcat(result,"\n");
                else {
                    if (values[j-1] >= h-(i-1)) strcat(result,"X");
                    else strcat(result," ");
                }
            }
    }
}

int main()
{
    int values1[10] = {1,0,3,1,2,4,5,6,2,2};
    int values2[3] = {1,0,1};
    int values3[6] = {3,4,1,0,2,3};
    char * formatted;
    char * example = "*****\n*X X*\n*****";
    histogram(formatted,values1, 10);
    printf("%s\n\n",formatted);

    histogram(formatted,values2,3);
    printf("%s\n",formatted);
    if (strcmp(example,formatted) == 0) printf("This matches EXACTLY and is correct");
histogram(formatted,values3,6);
printf("%s\n",formatted);
        return 0;
}