Nested if loop in Smallest positive number 2D Array in C - c

Question

I have this weird problem, When I run following code snippet, it gives me wrong answer. I am trying to find smallest positive number from 2D array.
I tried combining two if conditions in one if, placing brackets, interchanging if conditions. But while I debug I see, control never goes inside if greater than 0 condition.
float smallest(float b[3][4]);
int main()
{
float a[3][4],result;
int i, j;
printf("\nEnter 12 numbers into the array:\n");
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
scanf("%f", &a[i][j]);
}
printf("\n");
}
result=smallest(a);
printf("\nSamllest positive number is %.1f", result);
system("pause");
return 0;
}
float smallest(float b[3][4])
{
int i, j;
float min = b[0][0];
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
if (b[i][j]<min)
if (b[i][j]>0)
min = b[i][j];
}
}
return min;
}
Enter 12 numbers into the array:
-5
4
9
7
6
2
3
1
-7
5
4
7
Samllest positive number is -5.0

Answer 1

It is becuse you set min to b[0][0] which is -5 in your example, so the only number where if (b[i][j]<min) is true is -7. But your second if only true if the number is greater than 0. Which is false for -7, therefore min = b[i][j]; this code never executes.
Initialize min to FLT_MAX and it should be fine. (Although this could be problematic if the array only contains negative numbers.)

Answer 2

assign first positive value of array to your min and then use your code.
int check = 0;
int i, j;
float min=-2;//this is for case when all elements are negative
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
if (b[i][j] > 0)
{
min = b[i][j];
check = 1;
break;
}
}
if (check == 1)
break;
}
so your smallest function:
float smallest(float b[3][4])
{
int check = 0;
int i, j;
float min=-1;
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
if (b[i][j] > 0)
{
min = b[i][j];
check = 1;
break;
}
}
if (check == 1)
break;
}
if(min<0)
printf("no positive number");
else
{
for (i = 0; i < 3; i++)
{
for (j = 0; j < 4; j++)
{
if (b[i][j]<min)
if (b[i][j]>0)
min = b[i][j];
}
}
}
return min;
}
you also should check if returned min is navigate or positive in main.
if it was negative no positive value were found.

Answer 3

The function initially is defined incorrectly.
For starters the function shall have a second parameter that specifies the number of "rows" in the array. This function declaration
float smallest(float b[3][4]);
is equivalent to the following function declaration
float smallest(float b[][4]);
and the both declarations declare the same one function the declaration of which is adjusted by the compiler to the fol;lowing
float smallest(float ( *b )[4]);
Secondly the array can have no positive element. SO in this case the function will return an incorrect value.
Th function should return either an index or a pointer to the minimum positive elements. And if the index or the pointer is outside the array then it means that the array does not have a positive element.
Here is a demonstrative program that shows how the function can be defined and how in the caller there can be determine whether the array has a minimum positive element.
#include <stdio.h>
#define N 4
size_t smallest( float a[][N], size_t size )
{
size_t i = 0;
float *p = ( float * )a;
while ( i < size * N && !( 0 < p[i]) ) ++i;
size_t min = i;
for ( ++i; i < size * N; i++ )
{
if ( 0 < p[i] && p[i] < p[min] ) min = i;
}
return min;
}
int main(void)
{
float a[][N] =
{
{ -5, 4, 9, 7 },
{ 6, 2, 3, 1 },
{ -7, 5, 4, 7 }
};
const size_t M = sizeof( a ) / sizeof( *a );
size_t min = smallest( a, M );
if ( min < M * N )
{
printf( "The smallest positive element is %.1f\n", a[min / N][min % N] );
}
else
{
puts( "There ia no minimal positive element in the array" );
}
return 0;
}
The program output is
The smallest positive element is 1.0