Recreate strrchr() but getting extra characters at the end of string - c

Question

A task I have is to recreate the function strrchr. I figured out a way to iterate backward from the input given and stopping at the character I need to stop at, but the string came out backwards obviously. I already had created a function to reverse a string so I used that to reverse it back to normal. It works, but somewhere in my while loop when stopping at the character, it adds extra characters. Please help! I don't understand why!
#include <stdio.h>
#include <string.h>
// #include <stddef.h>
int
main () {
char* my_strrchr(char* param_1, char param_2)
{
int i = strlen(param_1) - 1;
int q = 0;
char new[strlen(param_1)];
char *new_ptr = new;
while (i >= 0) {
new[q] = param_1[i];
printf("%c\n", new[q]);
if (param_1[i] == param_2) {
i = 0;
}
i--;
q++;
}
int size = strlen(new_ptr) - 1;
for (int i = 0, q = size; i < q; i++, q--) {
char temp = new_ptr[i];
new_ptr[i] = new_ptr[q];
new_ptr[q] = temp;
}
printf("%s", new_ptr);
return (char *)new_ptr;
}
char *phrase = "C Language is HARD.";
char c = 'g';
my_strrchr(phrase, c);
return 0;
}

Answer 1

You don't need to do anything fancy. Just walk the string from the beginning, updating a variable with the address of the character you're looking for every time it's found, and return it when you hit the end of the string (Unlike strchr(), where you return after the first match). That way you only need one pass through the string instead of the two times it takes if you first find the length and then go backwards.
#include <stdio.h>
#include <stdlib.h>
// Really should return a const char*. Silly standard.
char *my_strrchr(const char *s, int c) {
const char *pos = NULL;
while (*s) {
if ((unsigned char)*s == (unsigned char)c) pos = s;
s++;
}
if (c == 0) {
// If searching for '\0', return a pointer to the one
// at the end of the string
return (char *)s;
} else {
return (char *)pos;
}
}
int main(void){
const char *foo = "the quite wet duck quacks a lot";
puts(my_strrchr(foo, 'q'));
return 0;
}