Informatics Olympiad 1.3: The control structure of the program (2)

​The first part of C++ language

Chapter III Program Control Structure

The second section switch statement

1049 I'm Not Afraid

#include <iostream>
using namespace std;

int main() {
    int day;
    cin >> day;

    switch (day) {
        case 1:
            cout << "NO" << endl;
            break;
        case 2:
            cout << "YES" << endl;
            break;
        case 3:
            cout << "NO" << endl;
            break;
        case 4:
            cout << "YES" << endl;
            break;
        case 5:
            cout << "NO" << endl;
            break;
        case 6:
            cout << "YES" << endl;
            break;
        case 7:
            cout << "YES" << endl;
            break;
    }

    return 0;
}

1050 Cycling and Walking

#include <iostream>
using namespace std;

int main() {
    int d;
    cin >> d;

    // 1/(1/1.2-1/3.0)=2
    int x = (27+23)*2;

    if (d > x) {
        cout << "Bike" << endl;
    }
    else if (d == x) {
        cout << "All" << endl;
    }
    else {
        cout << "Walk" << endl;
    }

    return 0;
}

1051 piecewise function

#include <cstdio>
using namespace std;

int main() {
    double x, y;
    scanf("%lf", &x);

    if (x>=0 && x<5) {
        y = -x + 2.5;
    }
    else if (x < 10){
        y = 2 - 1.5 * (x-3) * (x-3);
    }
    else if (x < 20) {
        y = x / 2 - 1.5;
    }

    printf("%.3lf\n", y);

    return 0;
}

1052 Calculate postage

#include <iostream>
#include <cmath>
using namespace std;

int main() {
    int w, cost;
    char urgent;
    cin >> w >> urgent;

    if (w <= 1000) {
        cost = 8;
    }
    else {
        w -= 1000;
        cost = 8 + ceil(w/500.0) * 4;
    }

    if (urgent == 'y') {
        cost += 5;
    }

    cout << cost << endl;

    return 0;
}

1053 Maximum number output

#include <iostream>
#include <cstdio>
using namespace std;

int main() {
    int a,b,c;
    cin >> a >> b >> c;

    if (a >= b && a >= c) {
        cout << a << endl;
    }
    else if (b >= a && b >= c) {
        cout << b << endl;
    }
    else {
        cout << c << endl;
    }

    return 0;
}

1054 Triangle Judgment

#include <iostream>
using namespace std;

int main() {
    int a,b,c;
    cin >> a >> b >> c;

    if (a+b>c && b+c>a && c+a>b) {
        cout << "yes" << endl;
    }
    else {
        cout << "no" << endl;
    }

    return 0;
}

1055 Judge Leap Year

#include <iostream>
using namespace std;

int main() {
    int year;
    cin >> year;

    if (year%4==0 && year%100!=0 || year%400==0) {
        cout << 'Y' << endl;
    }
    else {
        cout << 'N' << endl;
    }

    return 0;
}

The relationship between 1056 points and squares

#include <iostream>
#include <cmath>
using namespace std;

int main() {
    int x, y;
    cin >> x >> y;

    if (abs(x) <= 1 && abs(y) <= 1) {
        cout << "yes" << endl;
    }
    else {
        cout << "no" << endl;
    }

    return 0;
}

1057 Simple Calculator

#include <iostream>
using namespace std;

int main() {
    int a, b;
    char op;

    cin >> a >> b >> op;

    if (op == '+') {
        cout << a + b << endl;
    }
    else if (op == '-') {
        cout << a - b << endl;
    }
    else if (op == '*') {
        cout << a * b <<endl;
    }
    else if (op == '/') {
        if (b == 0) {
            cout << "Divided by zero!" << endl;
        }
        else {
            cout << a / b << endl;
        }
    }
    else {
        cout << "Invalid operator!" << endl;
    }

    return 0;
}

1058 Find the quadratic equation in one variable

#include <cstdio>
#include <cmath>
using namespace std;

int main() {
    double a, b, c, delta;
    scanf("%lf %lf %lf", &a, &b, &c);

    delta = b*b - 4*a*c;

    if (fabs(delta) < 1e-6) {
        printf("x1=x2=%.5lf\n", -b/(2*a));
    }
    else if (delta < 0){
        printf("No answer!\n");
    }
    else {
        if (a > 0) {
            printf("x1=%.5lf;x2=%.5lf\n", (-b-sqrt(delta))/(2*a), (-b+sqrt(delta))/(2*a) );
        }
        else {
            printf("x1=%.5lf;x2=%.5lf\n", (-b+sqrt(delta))/(2*a), (-b-sqrt(delta))/(2*a) );
        }
    }

    return 0;
}

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