Mark Mark - 1 year ago 59
C++ Question

Return a pointer to the last appearance of a character in a C-Style string (C++)

Return a pointer to the last appearance of c
appearing inside s and nullptr (0) if c does not appear inside s.

#include <string>
#include <iostream>
#include <cassert>
using namespace std;

const char* myStrRChr(const char* s, char c)
int curIdx = 0;
char last;

while (s[curIdx] != '\0')
if (s[curIdx] == c)
last = s[curIdx];
if (s[curIdx] == c)
return last;
// return '\0', nullptr, NULL
return "";

int main()
char cstr[50] = "Abadabadoo!";
char buf[10];
const char * cat = "cat";
char dog[] = "Labradoodle";

cout << "\nmyStrRChr(cstr, 'a') expects adoo!" << endl;
cout << " -- " << myStrRChr(cstr, 'a') << endl;

return 0;

This code returns "adabadoo!". I can't wrap my mind around as to how to get the last instance of "char c."

Answer Source

You can do this by obtaining a pointer to the end of the string and decrementing down the string searching for the character c, and a pointer to the beginning of the string to know where to stop looping:

const char *mystrrchr(const char *str, char c)
    int len = strlen(str);
    char *p = const_cast<char *>(&str[len-1]);
    char *stop = const_cast<char *>(&str[0]);
            return p;
    return nullptr;
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