#include <stdio.h>

int strend(const char *s, const char *t){
  int i = 0;
  int j = 0;

  while(*(s+i) != '\0'){
    i++;
  }
  while(*(t+j) != '\0'){
    j++;
  }

  if(j > i){
    return 0;
  }

  while(j >= 0){
    if(*(s+i) != *(t+j)){
      return 0;
    }
    i--;
    j--;
  }

  return 1;

}

char *strchr(const char *s, int c){
  char* lastOccurrence = NULL;
  int i = 0;
  while(*(s+i) != '\0'){

    if(*(s+i) == c){
      lastOccurrence = s+i;
    }

    i++;
  }

  return lastOccurrence;
}

char *strstr(const char *s, const char *t){
  int sizeT = 0, sizeS = 0;
  for(;*(t+sizeT) != '\0'; sizeT++){}
  for(;*(s+sizeS) != '\0'; sizeS++){}

  if(sizeT > sizeS){
    return NULL;
  }

  int valid;
  for(int i = 0; i <= sizeS-sizeT; i++){
    valid = 1;
    for(int j = 0; j < sizeT && valid; j++){
      if( *(s+i+j) != *(t+j) ){
    valid = 0;
      }
    }
    if(valid){
      return s+i;
    }
  }

  return NULL;
}

/*
int main(){
  int i = 0, j = 0;
  char str1[128];
  char str2[128];

  while( (str1[i] = getchar()) != '\n' ){
    i++;
  }
  str1[i] = '\0';
  while( (str2[j] = getchar()) != '\n' ){
    j++;
  }
  str2[j] = '\0';

  printf("Gelesene Strings\n");
  printf("1. : %s\n", str1);
  printf("2. : %s\n", str2);
  printf("Ergebnis: %s\n", strstr(str1, str2));

}
*/