Question

I have this homework assignment where the user is asked to input numbers and then calculates the mean median and mode, followed by asking if he/she wants to play again, and either repeating the program or quitting. Everything compiles, but I can seem to figure out the few things going wrong:

The mean works. the median doesn’t. If the array of ints has an even length, ie 4 numbers in the array, the median is supposed to be the middle two numbers averaged out. so if the numbers are ‘1, 3, 5, 6’ in order, then the median should be 4.000000. The mode doesn’t work either, and when asked to ‘play again?’ any answer causes the program to suddenly exit and crash. can someone help me find the error in my mean median mode calculations, and help me with the menu?

#define MAX 25
#include <stdio.h>
#include <stdbool.h>
#include <time.h>
#include <stdlib.h>

int readTotalNums();
void fillArray(int total, int nums[]);
void sortArray(int nums[], int total);
double findMean(int nums[], int total);
double findMedian(int nums[], int total);
int findMode(int nums[], int total);
void printResults(double mean, double median, double mode);
bool goAgain();

int main()  {
    int nums[MAX];
    int total;
    double mean, median, mode;
    do {
        total = readTotalNums(); //guarantee 1-25
        fillArray(total, nums); //read in the #s don't need to check range
        sortArray(nums, total);
        mean = findMean(nums, total);
        median = findMedian(nums, total);
        mode = findMode(nums, total);
        printResults(mean, median, mode);
    } while (goAgain());
    return 0;
}

int readTotalNums() {
    int num;
    do {
        printf("How many numbers? ");
        scanf("%i", &num);
    } while (num < 1 || num > 25);
    return num;
}

void fillArray(int total, int nums[]) {
    int temp;
    int i;
    printf("Please enter %i numbers\n", total);
    for (i = 0; i <= total-1; i++) {
        scanf("\n%i",&nums[i]);
    }
}

void sortArray(int nums[], int total) {
int x;
int y;
for(x=0; x<total; x++) {
    for(y=0; y<total-1; y++) {
        if(nums[y]>nums[y+1]) {
            int temp = nums[y+1];
            nums[y+1] = nums[y];
            nums[y] = temp;
        }
    }
}
}

double findMean(int nums[], int total) {
    int i;
    double sum = 0.0;
    for(i = 0; i < total; i++) {
        sum += nums[i];
    }
    return (sum/total);
}

double findMedian(int nums[], int total) {
    int temp;
    int i,j;
    for(i=0;i<total;i++)
        for(j=i+1;j<total;j++) {
            if(nums[i]>nums[j]) {
                temp=nums[j];
                nums[j]=nums[i];
                nums[i]=temp;
            }
        }
        if(total%2==0) {
            return (nums[total/2]+nums[total/2-1])/2;
        }else{
            return nums[total/2];
        }
}

int findMode(int nums[],int total) {
    int i, j, maxCount, modeValue;
    int tally[total];
    for (i = 0; i < total; i++) {
         tally[nums[i]]++;
    }
    maxCount = 0;
    modeValue = 0;
    for (j = 0; j < total; j++) {
        if (tally[j] > maxCount) {
            maxCount = tally[j];
            modeValue = j;
        }
    }
    return modeValue;
}

void printResults(double mean, double median, double mode) {
    printf("Mean: %d\tMedian: %d\tMode: %i", mean, median, mode);
}


bool goAgain() {
    char *temp;
    printf("\nWould you like to play again(Y/N)? ");
    scanf("%s", &temp);
    while (temp != 'n' && temp != 'N' && temp != 'y' && temp != 'Y') {
        printf("\nI am sorry that is invalid -- try again");
        printf("\nWould you like to play again(Y/N)? ");
        scanf("%s", &temp);
    }
    if (temp == 'y' || temp == 'Y') {
        return true;
    } else {
        return false;
    }
}

the output should be something like this:

How many numbers 4
Please enter 4 numbers
6
2
5
25
 Mean: 9.50 Median:  5.50   Mode:  2
Go again (y/n) n

Answer 1

Well, I found 3 problems:

1. Your printf is wrong. to print double, you should use %f. not %d or %i.
2. You should initialize tally before using.
3. In goAgain, temp should be char, and you should use %c instead of %s.