How to compare arrays in C - c

Question

I need to print the largest numbers in an array but my program keeps outputting the wrong numbers. What am i doing wrong?
int main(void)
{
int i, x,largest1,largest2, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
largest1 = 0;
largest2 = 0;
if (nums[i] > largest1)
largest1 = nums[i];
if (nums[x] > largest2)
largest2 = nums[x];
}
}
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", largest1, largest2);
system("pause");
}

Answer 1

Please check the data type of nums[i], its not an int. What you need is compare each value, say nums[i][x]
Do not initialize your largest number holder inside the loop. Otherwise, the largest number from previous iteration will be lost.
if the array contains all -ve numbers, initializing the highest number holder will 0 is faulty.
Check the below code[[ Tested on linux ]] for getting the idea. [For largest number only]
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
int main(void) {
int i, x,largest1, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
largest1 = INT_MIN;
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
if (nums[i][x] > largest1)
largest1 = nums[i][x];
}
}
printf("Largest number is %d\n", largest1);
return 0;
}
EDIT:
The code modification to include the second largest [and so on..] number display, is as per below logic
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
int main(void) {
int i, x,largest1,largest2, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
largest1 = INT_MIN;
largest2 = INT_MIN;
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
if (nums[i][x] > largest2)
largest2 = nums[i][x];
if ( largest2 > largest1)
{
largest2 = largest1;
largest1 = nums[i][x];
}
}
}
printf("Largest number is %d, second largest is %d\n", largest1, largest2);
return 0;
}

Answer 2

First of all, you should initialized largest1 and largest2 variables with the smallest possible integer values. Initializing them with 0 will give wrong result if all the numbers in your array are negative integers.
Also you should not re-initialize the largest1 and largest2 everytime you enter the inner loop.
I've corrected your code below. Please note that I've not tested the following code myself.
int i, x;
int largest1 = -32766;
int largest2 = -32767;
int nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
if (nums[i][x] > largest1) {
largest2 = largest1;
largest1 = nums[i][x];
} else if (num[i][x] > largest2) {
largest2 = num[i][x];
}
}
}
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", largest1, largest2);
system("pause");

Answer 3

Please make the following modifications. You have to access a 2-D array with 2 parameters to get that [x,y] value to compare.
int main(void) {
int i, x,largest1,largest2, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
largest1 = 0;
largest2 = 0;
if (nums[i][x] > largest1)
largest1 = nums[i][x];
if (nums[i][x] > largest2)
largest2 = nums[i][x];
}
}
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", largest1, largest2);
system("pause");
}
Hope it helps!
Please mark the answer right if its helpful and close the question.

Answer 4

You can move all the integer to a one dimensional array... then sort it. Then print the largest two element. Try this code...
#include<stdio.h>
#include<algorithm>
using namespace std;
int main(void) {
int i, x,largest1,largest2, save[30], j=0, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
save[j++]=nums[i][x];
}
}
sort(save,save+j);
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", save[j-1], save[j-2]);
system("pause");
}

Answer 5

Try this :
int main(void)
{
int i, x,largest1,largest2, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
largest1 = 0;
largest2 = 0;
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
if (nums[i][x] > largest1)
largest1 = nums[i][x];
if (nums[i][x] > largest2 && nums[i][x] < largest1)
largest2 = nums[i][x];
}
}
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", largest1, largest2);
system("pause");
}

Answer 6

everyone has already provided you with syntactically correct program.
just a slight addition (I thought may be this is what u wanted according to your prog) :
if (nums[i][x] > largest1)
{
largest2 = largest1;
largest1 = nums[i][x];
}
if (nums[i][x] > largest2)
largest2 = nums[i][x];
then largest1 and largest2 will have ur desired values.
and yeah, don't forget to initialize your initial values to lowest limit of int first.

Answer 7

Try this solution.
Here we are assigning new max value to largest1 and if we are getting again new max value we will assign old max value to largest2 , which will become the second largest value.
int main(void)
{
int i, x,largest1,largest2, nums[5][4] = { { 5, 6, 8, 9 }, { 3, -55, 6, 89 }, { 1023, 43, -2, 0 }, { 0, 12, 45, 12 }, { -4, 901, 34, 294 } };
largest1 = 0;
for (i = 0; i < 5; i++)
{
for (x = 0; x < 4; x++)
{
largest1 = 0;
largest2 = 0;
if (nums[i][x] > largest1){
largest2 = largets1; // assign last max value to `largest2`, it will be second max
largest1 = nums[i][x]; // getting new max value
}
}
}
printf("\n 1st largest: %d \n 2nd largest: %d \n\n", largest1, largest2);
system("pause");
}