Finding the minimum value in an array (What's wrong with my code?)

Question

This is for my intro to C++ course. We are currently doing arrays and I'm trying to find the min value for each column of the array. here is what I have:

#include <iostream>
using namespace std;    

int main(){
int grade[4][30] = {{76, 70, 80, 90, 100, 83, 61, 63, 64, 65, 97, 69, 70, 79,60, 70, 80, 90, 100, 83, 61, 63, 99, 98, 66, 69, 70, 79},
                    {74, 70, 80, 90,60, 61, 93, 88, 73, 65, 91, 69, 70, 79, 60, 70, 80, 90, 60, 83, 61, 63, 64, 65, 66, 69, 67, 74},
                    {72, 70, 80, 90, 99, 84, 62, 63, 99, 65, 66, 69, 70, 79, 60, 70, 80, 90, 99, 83, 61, 63, 64, 65, 66, 69, 70, 77},
                    {69, 70, 80, 90, 60, 61, 86, 63, 97, 97, 66, 69, 70, 79, 97, 70, 80, 90, 88, 83, 88, 63, 64, 65, 66, 69, 70, 79}};

int a;
for(int x = 0; x < 4; ++x){
    a = grade[x][0];
    for(int y = 0; y < 30; ++y){
        if( a > grade[x][y])
            a = grade[x][y];
            cout << "a is " << a << " for the " << y << "time" << endl;}
    cout << a << endl;}



return 0;

}

My problem is I don't understand why in the last two loops the value turns to 0? The real answer should be 60 for each row.

P.S I used this to find the maximum and it worked, but don't get why it won't work here?

How about writing a function that finds the minimum of a 1D array and then using that function to solve your problem for 2D arrays? Programming is all about writing functions. — user2100815
– user2100815, Commented Apr 30, 2017 at 16:42
Is this your code to find the minimum value? if not, please include that instead, as this looks to find the maximum value. I also agree with @NeilButterworth that a function to find result for a 1D would be useful — Graeme
– Graeme, Commented Apr 30, 2017 at 16:47
@Graeme: It's written misleadingly, but this actually does search for the minimum. It would probably be more apparent if he reversed the comparison to if (grade[x][y] < a) a = grade[x][y]; though. — Jerry Coffin
– Jerry Coffin, Commented Apr 30, 2017 at 16:48
@JerryCoffin Ah yeah I see it now. Doh! brain is half asleep it seems — Graeme
– Graeme, Commented Apr 30, 2017 at 16:58
@Graeme: If it's any comfort, I had an answer ready because a few minutes before, I'd started to write almost the same comment. — Jerry Coffin
– Jerry Coffin, Commented Apr 30, 2017 at 17:06

gmoniava · Accepted Answer · 2017-04-30 16:49:08Z

4

for(int y = 0; y < 30; ++y){

It is because for example your first array contains only 28 explicitly initialized elements and you iterate till 30 (see above). The elements which you didn't initialize yourself are initialized to 0.

edited Apr 30, 2017 at 16:49

answered Apr 30, 2017 at 16:46

gmoniava

28.9k9 gold badges61 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

aschepler · Accepted Answer · 2017-04-30 16:48:34Z

1

Your array initializers have less than 30 numbers. Since your array is declared to take 30 elements, the remaining entries are set to 0.

Since you don't appear to have 0s in your data, you could use 0 as a sentinel to know to stop the loop.

answered Apr 30, 2017 at 16:48

aschepler

72.5k11 gold badges114 silver badges174 bronze badges

Collectives™ on Stack Overflow

Finding the minimum value in an array (What's wrong with my code?)

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related