EX01

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("This is my first program!");
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("This is my second program!");
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("1 ");
    printf("2 ");
    printf("3 ");
    printf("4 ");
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("1 2 3 4 ");
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("%d %d %d %d", 1, 2, 3, 4);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("The number of minutes in 15 days is %d.", 15 * 24 * 60);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("180 minutes equal to %d hours.", 180 / 60);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("174 minutes: %d hours and %d minutes", 174 / 60, 174 % 60);
    return 0;
}

EX02

#include <stdio.h>

int main(int argc, char const *argv[]) {
    printf("Net price is 889 $, sales tax rate is 6%.\nSo the total purchase price is %f $.", 889 * 1.06);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float radius = 0, pi = 3.14159;
    printf("Please input radius:\n");
    scanf("%f", &radius);
    printf("The diameter of this circle is %f\n", radius * 2);
    printf("The circumference of this circle is %f\n", 2 * pi * radius);
    printf("The area of this circle is %f\n", pi * radius * radius);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float startingBalance, interestrate;
    printf("Interest calculation programnStarting balance ?\n");
    scanf("%f", &startingBalance);
    printf("Annual interest rate percntage ?\n");
    scanf("%f", &interestrate);
    printf("Balance after one year: %f", startingBalance * (1 + interestrate / 100));
    return 0;
}

EX03

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int grade = 0;
    printf("Input student's grade:\n");
    scanf("%d", &grade);
    if (grade >= 0 && grade < 60) {
        printf("Failed!");
    } else if (grade >= 60 && grade <= 100) {
        printf("Passed!");
    } else {
        printf("Error!");
    }
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int num = 0;
    printf("Please input an integer number:\n");
    scanf("%d", &num);
    if (num < 0) {
        num = -num;
    }
    if (num % 2 == 1) {
        printf("Odd number!");
    } else {
        printf("Even number!");
    }
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int a = 0, b = 0, c = 0;
    printf("Input three integer numbers.\nThe first:\n");
    scanf("%d", &a);
    printf("The second:\n");
    scanf("%d", &b);
    printf("The third:\n");
    scanf("%d", &c);
    a = a > b ? a : b;
    a = a > c ? a : c;
    printf("The largest number is %d", a);
    return 0;
}

EX04

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int day, month, year;
    printf("This program help you to transfer date.\n");
    while (true) {
        printf("Please input date: (For example: 1996 08 16)\n");
        scanf("%d %d %d", &year, &month, &day);
        if (year < 0 || month < 0 || month >12 || day < 0 || day >31) {
            printf("You have input an wrong date!\n");
            continue;
        }
        if ((month == 4 || month == 6 || month == 9 || month == 11) && day > 30) {
            printf("You have input an wrong date!\n");
            continue;
        }
        if (month == 2) {
            if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) {
                if (day > 29) {
                    printf("You have input an wrong date!\n");
                    continue;
                }
            }
            if (day > 28) {
                printf("You have input an wrong date!\n");
                continue;
            }
        }
        break;
    }
    switch (day) {
        case 1:
        case 21:
        case 31:
            printf("%dst ", day);
            break;
        case 2:
        case 22:
            printf("%dnd ", day);
            break;
        case 3:
        case 23:
            printf("%drd ", day);
            break;
        default:
            printf("%dth ", day);
    }
    switch (month) {
        case 1:
            printf("January ");
            break;
        case 2:
            printf("February ");
            break;
        case 3:
            printf("March ");
            break;
        case 4:
            printf("April ");
            break;
        case 5:
            printf("May ");
            break;
        case 6:
            printf("June ");
            break;
        case 7:
            printf("July ");
            break;
        case 8:
            printf("August ");
            break;
        case 9:
            printf("September ");
            break;
        case 10:
            printf("October ");
            break;
        case 11:
            printf("Novenber ");
            break;
        case 12:
            printf("December ");
    }
    printf("%d", year);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int total = 0, i = 2;
    printf("This program calculates 2+4+6+8+...+30.\n");
    while (i <= 30) {
        total += i;
        i += 2;
    }
    printf("The total is %d\n", total);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float sales = 0;
    while (true) {
        printf("Enter sales in pound(enter -1 to end):\n");
        scanf("%f", &sales);
        if(sales < 0) {
            break;
        } else {
            printf("Salary is %.2f\n", 200 + sales * 0.09);
        }
    }
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int pronum, quantity;
    float value;
    printf("Product Number    Retail Price(in pounds)\n             1    2.98\n             2    4.50\n             3    9.98\n             4    4.49\n             5    6.87\n");
    while (true) {
        printf("Please type in Product number and the quantity sold for one day: (-1 to end)\n");
        scanf("%d", &pronum);
        if (pronum < 0) {
            break;
        }
        scanf("%d", &quantity);
        switch (pronum) {
            case 1:
                value += 2.98 * quantity;
                break;
            case 2:
                value += 4.50 * quantity;
                break;
            case 3:
                value += 9.98 * quantity;
                break;
            case 4:
                value += 4.49 * quantity;
                break;
            case 5:
                value += 6.87 * quantity;
                break;
            default:
                printf("You have typed in wrong data!\n");
            }
    }
    printf("Total is %f", value);
    return 0;
}

EX05

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

int main(int argc, char const *argv[]) {
    int i = 1;
    do {
        printf("%4.0f\n", pow(2, i));
        i++;
    } while(i < 11);
    return 0;
}

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

int main(int argc, char const *argv[]) {
    for (int i = 0; i < 11; i++) {
        printf("%4.0f\n", pow(2, i));
    }
    return 0;
}

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

int main(int argc, char const *argv[]) {
    int num = 0, odd = 0, i = 0;
    double pi = 0;
    printf("This program calculates constant π by the infinite series:nπ=4-4/3+4/5-4/7+4/9-4/11...\nHow many terms do you want to calculate?\n");
    scanf("%d", &num);
    do {
        odd = 2 * i + 1;
        pi = pi + 4 / (pow(-1, i) * odd);
        i++;
    } while(i < num);
    printf("Result is %f\n", pi);
    return 0;
}

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

int main(int argc, char const *argv[]) {
    for (int i = 4; abs(i) <= 4; i--) {
        for (int j = 1; j <= abs(i); j++) {
            printf(" ");
        }
        for (int j = 1; j <= 9 - abs(i) * 2; j++) {
            printf("*");
        }
        printf("\n");
    }
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    for (int i = 1; i < 10; i++) {
        for (int j = 1; j <= i; j++) {
            printf("%d*%d=%2d", i, j, i * j);
        }
        printf("\n");
    }
    return 0;
}

EX06

#include <stdio.h>

void main(int argc, char const *argv[]) {
    int iNter = 0, round_to_nearest(float);
    float num = 0;
    while (true) {
        printf("This program will round the number you have input to the nearest integer.(Input 0 to exit)\nPlease input:\n");
        scanf("%f", &num);
        if (num == 0) {
            printf("Bye!");
            exit(0);
        } else if (num < 0) {
            num = -num;
            iNter = round_to_nearest(num);
            printf("%d\n", -iNter);
        } else {
            iNter = round_to_nearest(num);
            printf("%d\n", iNter);
        }
    }
}

int round_to_nearest(float n) {
    return (int) (n + 0.5);
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float larger(float, float);
    float a, b, c, d, e, f, total;
    printf("This program will ask you for three pairs of numbers, and will help you adds the larger of each pair.\nPlease input the first pair:(e.g. 9.99 10.01)\n");
    scanf("%f %f", &a, &b);
    printf("The second pair:\n");
    scanf("%f %f", &c, &d);
    printf("The third pair:\n");
    scanf("%f %f", &e, &f);
    total = larger(a, b) + larger(c, d) + larger(e, f);
    printf("Total is %f", total);
    return 0;
}

float larger(float x, float y){
    return (x > y ? x : y);
}

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

int main(int argc, char const *argv[]) {
    float time1, time2, time3, fee1, fee2, fee3, calcCharge(float);
    printf("This program help you calculate the parking charges for each of 3 customers.\nPlease input how many hours the first customer have parked car:(hours)\n");
    scanf("%f", &time1);
    printf("The second:\n");
    scanf("%f", &time2);
    printf("The third:\n");
    scanf("%f", &time3);
    if (time1 <= 0 || time2 <= 0 || time3 <= 0 || time1 >24 || time2 > 24 || time3 > 24) {
        printf("You have input wrong data! Please open this program again.\n");
    } else {
        fee1 = calcCharge(time1);
        fee2 = calcCharge(time2);
        fee3 = calcCharge(time3);
        printf("Car   Hours Charge\n");
        printf("1%10.1f%7.2f\n", time1, fee1);
        printf("2%10.1f%7.2f\n", time2, fee2);
        printf("3%10.1f%7.2f\n", time3, fee3);
        printf("TOTAL%6.1f%7.2f", time1 + time2 + time3, fee1 + fee2 + fee3);
    }
    return 0;
}

float calcCharge(float hours) {
    float charge;
    hours = (float) ceil(hours);
    charge = (hours + 1) * 0.5;
    if (charge < 2) {
        return 2;
    }
    if (charge > 10) {
        return 10;
    }
    return charge;
}

EX07

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int num, evenNum(int);
    printf("Please input an integer: (Crtl+Z to stop)\n");
    while (scanf("%d", &num) != EOF) {
        if (evenNum(num)) {
            printf("%d is an even number!\n", num);
        }
        printf("Next integer:\n");
    }
    return 0;
}

int evenNum(int a) {
    return (a + 1) % 2;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int a ,b, integerPower1(int, int);
    printf("Please input base and exponent:\n");
    scanf("%d %d", &a, &b);
    printf("Result is %d", integerPower1(a, b));
    return 0;
}

int integerPower1(int a, int b) {
    int sum = 1;
    for (int i = 1; i <= b; i++) {
        sum *= a;
    }
    return sum;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int a, b, integerPower2(int, int);
    printf("Please input base and exponent:\n");
    scanf("%d %d", &a, &b);
    printf("Result is %d", integerPower2(a, b));
    return 0;
}

int integerPower2(int m, int n) {
    if (!n) {
        return 1;
    } else {
        return m * integerPower2(m, n - 1);
    }
}

EX08

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int num[10];
    float avg = 0;
    for (int i = 0; i < 10; i++) {
        printf("Please input an integer:\n");
        scanf("%d", &num[i]);
    }
    for (int i = 0; i < 10; i++) {
        avg += num[i];
    }
    printf("Average is %f", avg / 10);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int a[2][5], max1, max2, min1, min2, max, min;
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 5; j++) {
            scanf("%d", &a[i][j]);
        }
    }
    max1 = min1 = a[0][0];
    for (int j = 0; j < 5; j++) {
        max1 = max1 > a[0][j] ? max1 : a[0][j];
        min1 = min1 < a[0][j] ? min1 : a[0][j];
    }
    max2  = min2 = a[1][0];
    for (int j = 0; j < 5; j++) {
        max2 = max2 > a[1][j] ? max2 : a[1][j];
        min2 = min2 < a[1][j] ? min2 : a[1][j];
    }
    max = max1 > max2 ? max1 : max2;
    min = min1 < min2 ? min1 : min2;
    printf("The maximum in row 1 is %d\n", max1);
    printf("The minimun in row i is %d\n", min1);
    printf("The maximum in row 2 is %d\n", max2);
    printf("The minimun in row 2 is %d\n", min2);
    printf("The maximun is %dn", max);
    printf("The minimun is %dn", min);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int i = 0, number[20];
    do {
        printf("Please type in an integer between 10 and 100 inclusive:\n");
        scanf("%d", &number[i]);
        if (number[i] >= 10 && number[i] <= 100) {
            if (i == 0) {
                i++;
                continue;
            }
            for (int j = 0; j < i; j++) {
                if (number[i] == number[j]) {
                    printf("Same number: %d\n", number[i]);
                    break;
                }
            }
        } else {
            continue;
        }
        i++;
    } while(i < 11);
    return 0;
}

EX09

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int dist[5];
    char towns[5][81], linein[81];
    for (int i = 0; i < 5; i++) {
        printf("Please type in the town's name and its distance to London:\n");
        gets(linein);
        sscanf(linein, "%s %d", towns[i], &dist[i]);
    }
    for (int i = 0; i < 5; i++) {
        if (dist[i] < 100) {
            printf("%s to London is less than 100 miles.\n", towns[i]);
        }
    }
    return 0;
}

#include <stdio.h>
#include <string.h>

int main(int argc, char const *argv[]) {
    int eofs;
    char linein[81];
    printf("Type in a string:\n");
    gets(linein);
    for (int i = 0; linein[i] != '\0'; i++) {
        eofs = i - 1;
    }
    for (int i = eofs; i >= 0; i--) {
        if (linein[i] == ' ') {
            for (int j = i + 1; linein[j] != '\0' && linein[j] != ' '; j++) {
                printf("%c", linein[j]);
            }
            printf(" ");
        }
    }
    for (int i = 0; linein[i] != '\0' && linein[i] != ' '; i++) {
        printf("%c", linein[i]);
    }
    printf("\n");
    for (int i = 0; linein[i] != '\0'; i++) {
        if (linein[i] == ' ') {
            for (int j = i - 1; j >= 0 && linein[j] != ' '; j--) {
                printf("%c", linein[j]);
            }
            printf(" ");
        }
    }
    for (int j = i - 1; j >= 0 && linein[j] != ' '; j--) {
        printf("%c", linein[j]);
    }
    printf("\n");
    for (int i = eofs; i >= 0; i--) {
        printf("%c", linein[i]);
    }
    return 0;
}

EX10

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int num[5], *p;
    for (int i = 0; i < 5; i++) {
        printf("Please type in an integer:\n");
        scanf("%d", &num[i]);
    }
    printf("First:\n");
    for (int i = 4; i >= 0; i--) {
        printf("%d\n", num[i]);
    }
    printf("Second:\n");
    for (int i = 0; i >= 0; i--) {
        printf("%d\n", *(num + i));
    }
    p = num;
    printf("Third:\n");
    for (int i = 0; i >= 0; i--) {
        printf("%d\n", p[i]);
    }
    printf("Fourth:\n");
    for (int i = 4; i >= 0; i--) {
        printf("%d\n", *(p + i));
    }
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float num[8], sum;
    for (int i = 0; i < 8; i++) {
        printf("Please type in a float number:\n");
        scanf("%f", &num[i]);
    }
    for (int i = 1; i < 8; i += 2) {
        printf("%d: %f\n", i + 1, *(num + i));
    }
    for (int i = 0; i < 8; i += 2) {
        sum += *(num + i);
    }
    printf("Sum is %f", sum);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int num[6], maxmin(int[], int);
    for (int i = 0; i < 6; i++) {
        printf("Please type in an integer:\n");
        scanf("%d", &num[i]);
    }
    maxmin(num, 6);
    return 0;
}

int maxmin(int number[], int n) {
    int max, min;
    max = min = number[0];
    for (int i = 1; i < n; i++) {
        max = max > number[i] ? max : number[i];
        min = min < number[i] ? min : number[i];
    }
    printf("max = %d\nmin = %d", max, min);
    return 0;
}

EX11

#include <stdio.h>

int main(int argc, char const *argv[]) {
    float annualSalary[5], monthlySalary[5];
    char name[5][81], linein[81];
    FILE *fp;
    for (int i = 0; i < 5; i++) {
        printf("Please type in employee's name and annual salary:\n");
        gets(linein);
        sscanf(linein, "%s %f", &name[i], &annualSalary[i]);
    }
    fp = fopen("salary.txt", "a+");
    fprintf(fp, "No.    Employee's Name Annual Salary   Monthly payment after tax\n");
    for (int i = 0; i < 5; i++) {
        monthlySalary[i] = annualSalary[i] / 12 * 0.8;
        fprintf(fp, "%2d     %15s   %13.3f  %25.3f\n", i + 1, name[i], annualSalary[i], monthlySalary[i]);
    }
    fclose(fp);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int distance[20];
    char line1[20][81], linein[81];
    FILE *fp;
    for(int i = 0; i < 20; i++) {
        printf("Please type in No.%2d town's name and the distance from London:\n", i + 1);
        gets(linein);
        sscanf(linein, "%s %d", &line1[i], &distance[i]);
    }
    fp = fopen("data.txt", "a+");
    fprintf(fp, "No.    Town's Name Distance from London\n");
    for(int i = 0; i < 20; i++) {
        fprintf(fp, "%2d     %11s   %20d\n", i + 1, line1[i], distance[i]);
    }
    fclose(fp);
    return 0;
}

#include <stdio.h>

int main(int argc, char const *argv[]) {
    int j, distance[20];
    char line1[20][81];
    FILE *input, *output;
    input = fopen("data.txt", "r");
    output = fopen("newdata.txt", "a+");
    fseek(input, 42, SEEK_SET);
    fprintf(output, "No.    Town's Name Distance from London\n");
    for(int i = 0; i < 20; i++) {
        fscanf(input, "%2d   %11s   %20d", &j, &line1[i], &distance[i]);
        if(distance[i] < 100) {
            fprintf(output, "%2d     %11s   %20d\n", i + 1, line1[i], distance[i]);
        }
    }
    fclose(input);
    fclose(output);
    return 0;
}