Code not assessing peaks correctly

Question

i have a code that prints out the number of peaks and their given magnitudes. the input is in the form of a single line that contains random integers separated by white space. a peak is only defined to be so when it is directly preceded and followed by a smaller value.
examples:

0 4 18 18 26 40 40 29 25 2 0         //has one peak of magnitude 40.

20 10 20         /*has no peaks, because both 20's are either not 

                   preceded or followed by a smaller number.*/

the code fails to behave correctly when the input data,

c

, begins with a declining set of numbers.
for example, the input:

9 8 7 6 5 4

returns a peak of "9", when it shouldn't return any magnitude.
another situation where it's behaving incorrectly is when we have the following input:

10 10 10 5 5 5 12 12 12 -1

. its returning a magnitude of "10", while again, it shouldn't return any magnitude because it doesn't fulfill the conditions of a peak .

the following is the code:

#include <stdio.h>

int main(void)

{



    int a = 0;

    int b = 0;

    int c = 0;

    int counter = 0;



    scanf("%d", &c);

    printf("Number  Magnitude\n");





    while (c >= 0){



        if ((b > a) && (b > c)) {     //to check if we have a peak     

            counter++;

            printf("%4d%11d\n", counter, b);

            a = b;

            b = c;

            scanf("%d", &c);



        }



        else if ((a < b) && (b == c)) {

            b = c;

            scanf("%d", &c);

        }   

        else {

            a = b;

            b = c;

            scanf("%d", &c);

        }       

    }



}

i prefer to keep the level of coding as minimum as possible, as i haven't done more than loops and if statements at this stage.

Answer 1

The issue is being caused because you initialize your boundary values to the minimum possible value. Any possible peak value will test positive when compared to that boundary value.

A small change fixes it, both boundary values should be set to a value that tests negative when compared to any possible peak value:

int a = INT_MAX;
int b = INT_MAX;

You will however to detect new lines and reset your values if you want to be able to do multiple lines of input, but I believe this is an existing problem

Code not assessing peaks correctly

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