September7.cpp

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

int exercise1(int num, int dig);
int exercise2a(int num1, int num2);
void exercise2b();
int exercise3a(int num);
void exercise3b();
int exercise4a(int num);
void exercise4b();
int exercise5a(int num);
void exercise5b();
void exercise6a(int num, int digit);
void exercise6b();
void exercise7a(int *num);
void exercise7b();
int exercise12(int num1, int num2, int num3);
void exercise22(int n);
int exercise32(int num);
int exercise42();
int exercise52(int num);
void exercise62(int *num1, int *num2);
int exercise72(int arr[], int length);
int exercise8(int arr[], int length);
void exercise9(int n);
void exercise10a(int from, int to);
void exercise10b();
int special_num(int num);
void exercise11();

int main()
{
    int ans, num1 = 13, num2 = 19, arr[] = {1, 2, 3, 4, 5}, len = sizeof(arr) / sizeof(int);
    srand(time(NULL));
    
    ans = exercise1(4204204, 4);
    printf("%d \n", ans);
    exercise2b();
    exercise3b();
    exercise4b();
    exercise5b();
    exercise6b();
    exercise7b();
    
    ans = exercise12(3, 3, 2);
    printf("%d \n", ans);
    exercise22(27);
    ans = exercise32(123);
    printf("%d \n", ans);
    ans = exercise42();
    printf("%d \n", ans);
    ans = exercise52(123321);
    printf("%d \n", ans);
    exercise62(&num1, &num2);
    exercise72(arr, len);
    exercise8(arr, len);
    exercise9(4);
    exercise10b();
    exercise11();

    return 0;
}

int exercise1(int num, int dig)
{
    int count = 0;

    while (num != 0)
    {
        if (num % 10 == dig) count++;
        num /= 10;
    }

    return count;
}

int exercise2a(int num1, int num2)
{
    return (rand() % (num2 - --num1)) + num1 + 1; 
}

void exercise2b()
{
    int num1, num2;

    scanf("%d %d", &num1, &num2);

    while (num1 != -999 && num2 != -999) 
    {
        for (int i = 0; i < 5; i++) printf("%d \n", exercise2a(num1, num2));
        scanf("%d %d", &num1, &num2);
    }
}

int exercise3a(int num)
{
    int sum = 0;

	while (num != 0)
	{
		sum += num % 10;
		num /= 10;
	}

    return sum;
}

void exercise3b()
{
    int n, num, permnum, sum = 0, res;

    scanf("%d", &n);

    for (int i = 0; i < n; i++)
    {
        scanf("%d", &num);
        
        res = exercise3a(num);

        if (res >= sum || i == 0)
        {
            permnum = num;
            sum = res;
        }
    }

    printf("The last number with the biggest sum of digits is %d with a sum of %d \n", permnum, sum);
}

int exercise4a(int num)
{
    int cur = 1, sum = 0;

    while (cur != num && num > 1) 
    {
        if (num % cur == 0) sum += cur;
        cur++;
    }

    return (num == sum);
}

void exercise4b() { for (int i = 10; i <= 1000; i++) if (exercise4a(i)) printf("%d \n", i); }

int exercise5a(int num)
{
    int digit, temp;

    while (num != 0)
    {
        digit = num % 10;
        num /= 10;
        temp = num;
        while (digit != (temp % 10) && temp > 0) temp /= 10;
        if (temp > 0) return 0;
    }

    return 1;
}

void exercise5b()
{
    int ans = 0, num, count = 0;
    
    while (!ans)
    {
        scanf("%d", &num);
        count++;
        ans = exercise5a(num);
    }

    printf("good number was %d and %d numbers were tested before it \n", num, --count);
}

void exercise6a(int num, int digit)
{
    int count = 0;

    for (int i = 1; num > 0; i++)
    {
        if (num % 10 == digit)
        {
            printf("%d ", i);
            count++;
        } 
        num /= 10;
    }

    printf((count == 0) ? "0 \n \n" : "\n \n");
}

void exercise6b()
{
    int num;

    scanf("%d", &num);

    for (int i = 0; i <= 9; i++)
    {
        printf("%d \n", i);
        exercise6a(num, i);
    }
}

void exercise7a(int *num)
{
    int mul = 1;

    while (*num / mul != 0)
    {
        if ((*num / mul) % 10 == 1)
        {
            *num -= mul;
            *num += mul / 10;
        }

        mul *= 10;
    }
}

void exercise7b()
{
    int num, n;

    scanf("%d %d", &num, &n);

    while (n-- > 0 && num <= 1111) exercise7a(&num);

    printf("%d \n", num);
}

int exercise12(int num1, int num2, int num3) { return (num1 == num2) && (num2 == num3); }

void exercise22(int n) { for (int i = 1; i < n; i++) if (i % 3 == 0) printf("%d \n", i); }

int exercise32(int num)
{
    int count = 0;
    
    while (num > 0)
    {
        count++;
        num /= 10;
    }

    return count;
}

int exercise42()
{
    char ch;

    int ans = 0;

    while((ch = getchar()) != '*')
    {
        if (ch == EOF || ch == '\n') continue;
        ans *= 10;
        ans += (int)ch - 48;
    }

    return ans;
}

int exercise52(int num)
{
    int mul1 = 1, mul2 = 1;

	while (num / mul1 > 10) mul1 *= 10;
	
	int dig1 = num % 10, dig2 = num / mul1;

	while (1)
	{
		if (dig1 != dig2) return 0;
		else if (mul1 == mul2 || mul1 == mul2 * 10) return 1;

		mul1 /= 10;
		mul2 *= 10;

		dig1 = (num / mul2) % 10;
		dig2 = (num / mul1) % 10;
	}
}

void exercise62(int *num1, int *num2)
{
    if (num2 > num1)
    {
        int temp = *num1;
        *num1 = *num2;
        *num2 = temp;
    }
}

int exercise72(int arr[], int length)
{
    int count = 0;

    for (int i = 0; i < length; i++) if (i > 0 && arr[i] > arr[i - 1]) count++;

    return count;
}

int exercise8(int arr[], int length)
{
    for (int i = 0; i < length; i++) if (arr[i] > 99 || arr[i] < 10) return 0;
    return 1;
}

void exercise9(int n)
{
    int layer = 0;

    while (layer++ < n)
    {
        for (int i = layer; i >= 1; i--) printf("%d ", i);
        for (int i = 2; i <= layer; i++) printf("%d ", i);
        printf("\n");
    }
}

void exercise10a(int from, int to) { for (int i = from; i < to; i++) if ((i / 100) + ((i / 10) % 10) == pow(i % 10, 2)) printf("%d \n", i); }

void exercise10b() { exercise10a(500, 600); }

int special_num(int num)
{
    int ans = 0, original = num;

    while (num != 0)
	{
		ans *= 10;
		ans += num % 10;
		num /= 10;
	}

    return (original * 4 == ans);
}

void exercise11()
{
    int count = 0;
    for (int i = 1000; i < 10000; i++) if (special_num(i)) count++;
    printf("There are %d special numbers with 4 digits \n", count);
}