Where is the logic wrong in my code?

Question

Sorry for my english.

I am taking an introductory course in C, and I have some problems with the logic of my program. He will sometimes produce the required output.

The task is to write a function that takes the elements of the array, to return the largest even digit in the element.

int ary1[] = {123, 456, -7890, 12}; Would -7890 as the largest value with 8 as the largest even number and its occurrences.
int ary2[5] = {-123, 654, 78, 15, 189}; Would return 189 as the largest value with 8 as the largest even number and its occurrences.
int ary3[2] = {9, 9}; Would not return anything.
int ary4[] = {123, 123, 0, 12}; Would return 123 as the largest value, with 2 as the largest even digit and its occurrences.
int ary5[] = {24, 45, -789, 24, 1}; Would -789 as the largest value with 8 as the largest even number and its occurrences.
int ary6[] = {-749, -241, 1, 45}; Would return 45 as the largest value, with 4 as the largest even number and its occurrences.

Here is my code:

 #include <stdio.h> void digitExtract(int[], int); int main() { int ary1[] = { 123, 456, -7890, 12 }; int ary2[5] = { -123, 654, 78, 15, 189 }; int ary3[2] = { 9, 9 }; int ary4[] = { 123, 123, 0, 12 }; int ary5[] = { 24, 45, -789, 24, 1 }; int ary6[] = { -749, -241, 1, 45 }; int ary7[] = { 1, 3, 5 }; printf("\nCalling function in ary1[]:\n"); digitExtract(ary1, 4); printf("\nCalling function in ary2[]:\n"); digitExtract(ary2, 5); printf("\nCalling function in ary3[]:\n"); digitExtract(ary3, 2); printf("\nCalling function in ary4[]:\n"); digitExtract(ary4, 4); printf("\nCalling function in ary5[]:\n"); digitExtract(ary5, 5); printf("\nCalling function in ary6[]:\n"); digitExtract(ary6, 4); printf("\nCalling function in ary7[]:\n"); digitExtract(ary7, 3); } void digitExtract(int Array[], int array_size) { int tempValue; int x; int myArr[10] = { 0 }; int evenCount = 0; int max = Array[0]; for (int i = 1; i < array_size; i++) { if (Array[i] < 0) { Array[i] = -Array[i]; if (Array[i] > max) { max = Array[i]; } } } tempValue = (max < 0) ? -max : max; do { myArr[tempValue % 10]++; tempValue /= 10; } while (tempValue != 0); for (x = 8; x > 0; x -= 2) { if (myArr[x]>0) { printf("Displaying from inside of function():\n"); printf("\nThe largest even digit: %d\n", x ); printf("\nThe digit %d occurs %d times.\n", x, myArr[x]); evenCount++; break; } } if (evenCount == 0) printf("\nNo even digits found!\n\n"); } 

I know that there is an error in my logic, since for ary2[] it gives an even number 6 , and it occurs when it should be 8 , but I do not know where.

The function will work for an array with odd values ​​as its element.

Where or what am I doing wrong?

Thanks.

Answer 1

Your task is to find the largest even digit, and then find the largest value that this digit has ... not find the largest value, and then find the largest even digit inside it.

I would start by writing a function called max_even_digit to work with a single int , and then check this out and work from there.

 int max_even_digit(int x) { int max = 0; while (x) { int digit = x % 10; digit = digit < 0 ? -digit : digit; if (x % 2 == 0 && digit > max) { max = digit; } x /= 10; } return max; } 

Once you do, move your array as if you were finding the maximum value, but let the return value max_even_digit take precedence over the actual value.

 int max_even_digit_value(int *array, size_t array_size) { if (array_size == 0) { return 0; } int max = array[0]; for (size_t x = 0; x < array_size; x++) { int a = max_even_digit(array[x]), b = max_even_digit(max); if (a > b || (a == b && array[x] > max)) { max = array[x]; } } return max; }