Finding lowest/highest values in 2D array

[halopower67]

Hey guys, any idea as to how to find the lowest value and the highest value in this 2D array? I made the functions to find the lowest and highest, but all im getting on execution is a 1 on both, no matter what number i input.

Here's my code

#include <cstdlib>
#include <iostream>

using namespace std;

const int MONKEYS = 3;
const int DAYS = 7;
double average = 0;

int getSum (int [][DAYS]);
void getChart (int [][DAYS]);
void dayAvg (int table [][DAYS]);
int findLowest (int table [][DAYS]);
int findHighest (int table [][DAYS]);

int main(int argc, char *argv[])
{
    int table [MONKEYS][DAYS];
    
    cout << "The diet of 3 monkeys over 7 days, please input your info: \n\n";
    
    getChart(table);
    
    cout << "The total amount of food consumed by the monkeys: "
         << getSum(table) << " Pounds\n\n";
         
    dayAvg(table);
    
    cout << "The lowest amount of food eaten was: " << findLowest(table) << " Pounds\n";
    cout << "The highest amount of food eaten was: " << findHighest(table) << " Pounds\n";
    
    //ofstream outData;
    //outData.open("results.txt");
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

int getSum (int table [][DAYS])
{
    int sum = 0;
    for ( int monkey = 0;  monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
            sum += table [monkey][day];
    }
    return sum;
}

void getChart (int table[][DAYS])
{
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            cout << "Monkey " << (monkey+1) << ", ";
            cout << "Day " << (day+1) << ": ";
            cin >> table [monkey][day];
        }
        cout << endl;
    }
}

void dayAvg (int table [][DAYS])
{
    for ( int day = 0;  day < DAYS; day++)
    {
        int total = 0;
        for (int monkey = 0; monkey < MONKEYS; monkey++)
        {
            total += table [monkey][day];
        }
        average = total/MONKEYS;
        cout << "Average food consumed on day " << (day+1)
             << " by all 3 monkeys is: " << average << " Pounds" << endl;
    }
}

int findLowest (int table [][DAYS])
{
    int lowest = table [MONKEYS][DAYS];
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            if (table [monkey][day] < lowest)
                lowest = table[MONKEYS][DAYS];
        }
        
        cout << endl;
    }
    return lowest;
}

int findHighest (int table [][DAYS])
{
    int highest = table [MONKEYS][DAYS];
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            if (table [monkey][day] > highest)
                highest = table[MONKEYS][DAYS];
        }
        
        cout << endl;
    }
    return highest;
}

[coder777]

that's because

lowest = table[MONKEYS][DAYS]; highest = table[MONKEYS][DAYS];

whenever you assing lowest/highest you use the array sizes which points beyond the end instead of the valid index

[halopower67]

This is what im having problems with, when i apply the lowest = table[monkey][day]; to my code, it doesn't work for finding the lowest, but it works for finding the highest. Heres my complete code, the problem is that it is still not finding the lowest:

#include <cstdlib>
#include <iostream>

using namespace std;

const int MONKEYS = 3;
const int DAYS = 7;
double average = 0;

int getSum (int [][DAYS]);
void getChart (int [][DAYS]);
void dayAvg (int table [][DAYS]);
int findLowest (int table [][DAYS]);
int findHighest (int table [][DAYS]);

int main(int argc, char *argv[])
{
    int table [MONKEYS][DAYS];
    
    cout << "The diet of 3 monkeys over 7 days, please input your info: \n\n";
    
    getChart(table);
    
    cout << "The total amount of food consumed by the monkeys: "
         << getSum(table) << " Pounds\n\n";
         
    dayAvg(table);
    
    cout << "The lowest amount of food eaten : " << findLowest(table) << " Pounds\n";
    cout << "The highest amount of food eaten : " << findHighest(table) << " Pounds\n";
    
    //ofstream outData;
    //outData.open("results.txt");
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

int getSum (int table [][DAYS])
{
    int sum = 0;
    for ( int monkey = 0;  monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
            sum += table [monkey][day];
    }
    return sum;
}

void getChart (int table[][DAYS])
{
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            cout << "Monkey " << (monkey+1) << ", ";
            cout << "Day " << (day+1) << ": ";
            cin >> table [monkey][day];
        }
        cout << endl;
    }
}

void dayAvg (int table [][DAYS])
{
    for ( int day = 0;  day < DAYS; day++)
    {
        int total = 0;
        for (int monkey = 0; monkey < MONKEYS; monkey++)
        {
            total += table [monkey][day];
        }
        average = total/MONKEYS;
        cout << "Average food consumed on day " << (day+1)
             << " by all 3 monkeys is: " << average << " Pounds" << endl;
    }
}

int findLowest (int table [][DAYS])
{
    int lowest = table [MONKEYS][DAYS];
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            if (table [monkey][day] < lowest)
                lowest = table[monkey][day];
        }
        
        cout << endl;
    }
    return lowest;
}

int findHighest (int table [][DAYS])
{
    int highest = table [MONKEYS][DAYS];
    for (int monkey = 0; monkey < MONKEYS; monkey++)
    {
        for (int day = 0; day < DAYS; day++)
        {
            if (table [monkey][day] > highest)
                highest = table[monkey][day];
        }
        
        cout << endl;
    }
    return highest;
}

[xephon]

i just tried your code. seems the problem is at the initialization at line 81.

table[MONKEYS][DAYS] does not exist as index starts from 0 to MONKEYS-1 and DAYS-1. thus, it should be initialized as 0.

if you initialize it with table[MONKEYS-1][DAYS-1] or even findHighest(table), the return will be correct.

[halopower67]

Yeah i just initialized line 81 to table [0][0] and it works now, but im wondering why i dont have to do that to line 97 as well?

[halopower67]

Also, now that this is working, how could i write all this information to a file? could it be done with one function? or would it have to be implemented on every function i do?

[xephon]

coz if it's initialize to 0 at line 97, any value would be greater. thus the program proceeds correctly.

u can try this: does not change ur original line 81, but put a -1 in the table. this time the return for findlowest is -1. same if u put all negative to the table, the return for findHighest would be 0.

this gives u an insight of how arrays are initialized.

[coder777]

xephon wrote:

table[MONKEYS][DAYS] does not exist as index starts from 0 to MONKEYS-1 and DAYS-1. thus, it should be initialized as 0.

no it's a random number (probably negative)

line 81: should be int lowest = INT_MAX; include limits.h
line 97: should be int highest = 0;

EDIT: line 97 is highest of course

[xephon]

@coder777

keep close to declarations. as input are set to be table [][DAYS], from line 10 to 14, the newer compilers will recognize it as a dynamic array. even it's not allowed initially for C++, certain compilers will "reserve" spaces for upcoming rows at table[MONKEYS]. and initialization for these reserves are 0. i'm not saying this is true in all case, but is possible in a lot cases.

also, line 81 does not have to initialize as this. using a member within the data structure, which is likely in register, is faster than call INT_MAX, which is definitely not in register.

[coder777]

don't rely on the 'reserve space'. never provoke an error that might or might not occur. those are the most difficult to find.

INT_MAX is a #define of the highest int number (2147483647).

xephon wrote:

using a member within the data structure

members? within what data structure?

[xephon]

@coder777

I was actually thinking this: before the function call jump to designated mem location for findHighest and findLowest, which data IS in mem cache at that moment. INT_MAX is not, so the system would go and grab it. but in this case, as after assigning the last data in table, that is table[MONKEYS-1][DAYS-1], it is not likely have been replaced and erased from the cache yet. Thus, as a cache hit is faster than a cache miss which INT_MAX results, it should be faster to assign table[MONKEYS-1][DAYS-1].

If you have any information proving above is not true, please let me know. I'd like some reference as well. I always believe the above is right, so it would be good to know if I got it wrong. With certain proof of course.

Also, this may be a little out of the topic. So if you'd like continue this discussing elsewhere like PM or through e-mail, you are certainly welcome.

[sohguanh]

If you are allowed to use standard C++ algorithm classes, you can amend your 2D array a bit (as in make it like one long list of elements) to call below functions.

http://www.cplusplus.com/reference/algorithm/min_element/

http://www.cplusplus.com/reference/algorithm/max_element/