!lezione-9.md

Esercizi Lezione 9

da-numero-a-stringa.c

#include <stdio.h>
#include <stdlib.h>

void print_numero(int n) {
  char *exp0[] = {
    "",
    "uno",
    "due",
    "tre",
    "quattro",
    "cique",
    "sei",
    "sette",
    "otto",
    "nove"
  };
  
  char *exp1[] = {
    "",
    "",
    "vent",
    "trent",
    "quarant",
    "cinquant",
    "sessant",
    "settant",
    "ottant",
    "novant"
  };
  
  char *deci[] = {
    "dieci",
    "undici",
    "dodici",
    "tredici",
    "quattordici",
    "quindici",
    "sedici",
    "diciassette",
    "diciotto",
    "diciannove"
  };
  
  if (n > 9 && n < 20) {
    printf(deci[n % 10]);
    return;
  }
  
  printf("%s", exp1[(n / 10) % 10]);
  
  if (n % 10 != 1 && n % 10 != 8) {
    if ((n / 10) % 10 == 2) {
      printf("i");
    }
    else if ((n / 10) % 10 > 2) {
      printf("a");
    }
  }
  
  printf("%s", exp0[n % 10]);
}

int main() {
  
  int value;
  scanf("%d", &value);
  
  print_numero(value);
  
}

esercizio-conta-occ.c

#include <stdio.h>
#include <stdlib.h>

int main() {
  
  char str[40];
  int i = 0;
  
  while(i < 40 && str[i - 1] != '\n') {
    str[i++] = getchar();
  }
  
  char target = getchar();
  
  int occ = 0;
  
  for (int i = 0; i < 40; i++) {
    if (str[i] == target) 
      occ++;
  }
  
  printf("%d\n", occ);
  
}

esercizio-fibonacci.c

#include <stdio.h>
#include <math.h>

int fibonacci(int n) {
  
  double sqrt5 = sqrt(5.0);
  double phi = (1.0 + sqrt5) * 0.5;
  
  return (int) ((pow(phi, n) - pow(-phi, -n)) / sqrt5);
  
}

int main() {
  
  int n;
  
  scanf("%d", &n);
  
  printf("%d\n", fibonacci(n));
  
}

esercizio-prime-palindrome.c

#include <stdio.h>
#include <stdlib.h>

int is_palindrome(char * string, int size) {
  if (size > 1) {
    if (string[0] == string[size - 1]) {
      return is_palindrome(&string[1], size - 2);
    }
    else {
      return 0;
    }
  }
  else {
    return 1;
  }
}

void read_str(char * str, int * size, int maxSize) {
  
  while(*size < maxSize && str[*size - 1] != '\n') {
    str[(*size)++] = getchar();
  }
  
  str[--(*size)] = '\0';
  
}

int main() {
  
  int count;
  
  scanf("%d", &count);
  
  char *strings = malloc(sizeof(char) * 40 * count);
  int *sizes = malloc(sizeof(int) * count);
  
  getchar();
  
  for (int i = 0; i < count; i++) {
    read_str(strings + i * 40, sizes + i, 40);
  }
  
  for (int i = 0; i < count; i++) {
    if (is_palindrome(strings + i * 40, *(sizes + i))) 
      printf("%s\n", strings + i * 40);
  }
  
  for (int i = 0; i < count; i++) {
    // printf("'%s'\n", *(strings + i * 40));
    if (!is_palindrome(strings + i * 40, *(sizes + i))) 
      printf("%s\n", strings + i * 40);
  }
  
}

esercizio-reverse.c

#include <stdio.h>
#include <stdlib.h>

void swap(char * a, char * b) {
  char tmp = *b;
  *b = *a;
  *a = tmp;
}

void reverse(char * string, int size) {
  if (size > 1) {
    swap(&string[0], &string[size - 1]);
    reverse(&string[1], size - 2);
  }
}

int main() {
  
  char str[40];
  int size = 0;
  
  while(size < 40 && str[size - 1] != '\n') {
    str[size++] = getchar();
  }
  
  str[--size] = '\0';
  
  // printf("'%s', size=%d\n", str, size);
  
  reverse(str, size);
  
  // printf("'%s', size=%d\n", str, size);
  
  printf("%s", str);
  
}