第2讲 判断语句

#include 

using namespace std;

int main()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    
    if (b > c && d > a && c + d > a + b && c > 0 && d > 0 && a % 2 == 0)
        cout << "Valores aceitos" << endl;
    else 
        cout << "Valores nao aceitos" << endl;
    
	return 0;
}

#include 
#include 
#include 

using namespace std;

int main()
{
    double a, b, c;
    cin >> a >> b >> c;
    
    double delta = b * b - 4 * a * c;
    if (delta < 0 || !a) cout << "Impossivel calcular" << endl;
    else
    {
        printf("R1 = %.5lfn", (- b + sqrt(delta)) / (2 * a));
        printf("R2 = %.5lfn", (- b - sqrt(delta)) / (2 * a));
    }
    
	return 0;
}

#include 

using namespace std;

int main()
{
	double x;
	cin >> x;
	
	if (x >= 0 && x <= 25) cout << "Intervalo [0,25]" << endl;
	else if (x > 25 && x <= 50) cout << "Intervalo (25,50]" << endl;
	else if (x > 50 && x <= 75) cout << "Intervalo (50,75]" << endl;
	else if (x > 75 && x <= 100) cout << "Intervalo (75,100]" << endl;
	else cout << "Fora de intervalo" << endl;
    
	return 0;
}

#include 

int main()
{
    int x, y;
    double p[] = {0, 4, 4.5, 5, 2, 1.5};
    scanf("%d %d", &x, &y);
    
    printf("Total: R$ %.2lfn", p[x] * y);
    
	return 0;
}

#include 
#include 

using namespace std;

int main()
{
    double n1, n2, n3, n4, x, y, z;
    cin >> n1 >> n2 >> n3 >> n4;
    
    x = 0.2 * n1 + 0.3 * n2 + 0.4 * n3 + 0.1 * n4;
    printf("Media: %.1lfn", x);
    
    if (x >= 7) puts("Aluno aprovado.");
    else if (x >= 5)
    {
        puts("Aluno em exame.");
        cin >> y;
        printf("Nota do exame: %.1lfn", y);
        z = (x + y) / 2;
        if (z >= 5) puts("Aluno aprovado.");
        else puts("Aluno reprovado.");
        printf("Media final: %.1lfn", z);
    }
    else puts("Aluno reprovado.");
    
	return 0;
}

#include 

using namespace std;

int main()
{
    double x, y;
    cin >> x >> y;
    
    if (x > 0 && y > 0) cout << "Q1" << endl;
    else if (x > 0 && y < 0) cout << "Q4" << endl;
    else if (x < 0 && y > 0) cout << "Q2" << endl;
    else if (x < 0 && y < 0) cout << "Q3" << endl;
    else if (y) cout << "Eixo Y" << endl;
    else if (x) cout << "Eixo X" << endl;
    else cout << "Origem" << endl;
    
	return 0;
}

#include 
#include 

using namespace std;

int main()
{
    int a[3], b[3];
    
    for (int i = 0 ; i < 3; i ++ )
    {
        cin >> a[i];
        b[i] = a[i];
    }
    
    sort(a, a + 3);
    
    for (int i = 0 ; i < 3; i ++ ) cout << a[i] << endl;
    cout << endl;
    for (int i = 0 ; i < 3; i ++ ) cout << b[i] << endl;

	return 0;
}

#include 
#include 

using namespace std;

int main()
{
	double a, b, c;
	cin >> a >> b >> c;
	
	if (a + b > c && a + c > b && b + c > a)
		printf("Perimetro = %.1lfn", a + b + c);
	else
		printf("Area = %.1lfn", (a + b) * c / 2);
		
	return 0;
}

#include 

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    
    if (a % b == 0 || b % a == 0)
        cout << "Sao Multiplos" << endl;
    else
        cout << "Nao sao Multiplos" << endl;
        
	return 0;
}

#include 
#include 
#include 

using namespace std;

int main()
{
    double a, b, c;
    cin >> a >> b >> c;
    
    if (a < b) swap(a, b);
    if (a < c) swap(a, c);
    if (b < c) swap(b, c);
    
    if (a >= b + c) cout << "NAO FORMA TRIANGULO" << endl;
    else
    {
        if (a * a == b * b + c * c) cout << "TRIANGULO RETANGULO" << endl;
        else if (a * a > b * b + c * c) cout << "TRIANGULO OBTUSANGULO" << endl;
        else if (a * a < b * b + c * c) cout << "TRIANGULO ACUTANGULO" << endl;
        if (a == b && b == c) cout << "TRIANGULO EQUILATERO" << endl;
        else if(a == b || b == c) cout << "TRIANGULO ISOSCELES" << endl;
    }
    
	return 0;
}

#include 
#include 

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    
    cout << "O JOGO DUROU "<< (b - a <= 0 ? b - a + 24 : b - a) << " HORA(S)" << endl;
    
	return 0;
}

#include 

using namespace std;

int main()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    
    int t = (c * 60 + d) - (a * 60 + b);
    if (t <= 0) t += 24 * 60;
    
    cout << "O JOGO DUROU " << t / 60 << " HORA(S) E " << t % 60 << " MINUTO(S)" << endl;
	
	return 0;
}

#include 
#include 

using namespace std;

int main()
{
    double salary;
    int rate;
    cin >> salary;
    
    if (salary <= 400) rate = 15;
    else if (salary <= 800) rate = 12;
    else if (salary <= 1200) rate = 10;
    else if (salary <= 2000) rate = 7;
    else rate = 4;
    
    printf("Novo salario: %.2lfn", salary + salary * rate / 100);
    printf("Reajuste ganho: %.2lfn", salary * rate / 100);
    printf("Em percentual: %d %%n", rate);
    
	return 0;
}

• 输出百分号 printf("%%");

#include 
#include 

using namespace std;

int main ()
{
    string s1, s2, s3;
    cin >> s1 >> s2 >> s3;
    
    if (s1 == "vertebrado")
    {
        if (s2 == "ave")
        {
            if (s3 == "carnivoro") cout << "aguia" << endl;
            else cout << "pomba" << endl;
        }
        else
        {    
            if (s3 == "onivoro") cout << "homem" << endl;
            else cout << "vaca" << endl;
        }
    }
    else
    {
        if (s2 == "inseto")
        {
            if (s3 == "hematofago") cout << "pulga" << endl;
            else cout << "lagarta" << endl;
        }
        else
        {
            if (s3 == "hematofago") cout << "sanguessuga" << endl;
            else cout << "minhoca" << endl;
        }
    }
    
	return 0;
}

#include 
using namespace std;

int main()
{
    int num;
    cin >> num; 
    
    switch (num)
    {
        case 61:
            cout << "Brasilia" << endl;
            break;
        case 71:
            cout << "Salvador" << endl;
            break;
        case 11:
            cout << "Sao Paulo" << endl;
            break;
        case 21:
            cout << "Rio de Janeiro" << endl;
            break;
        case 32:
            cout << "Juiz de Fora" << endl;
            break;
        case 19:
            cout << "Campinas" << endl;
            break;
        case 27:
            cout << "Vitoria" << endl;
            break;
        case 31:
            cout << "Belo Horizonte" << endl;
            break;
        default:
            cout << "DDD nao cadastrado" << endl;
            break;
    }
    
	return 0;
}

#include 
#include 

using namespace std;

int main()
{
    double salary, tax = 0;
    cin >> salary;
	
    if (salary > 4500)
    {
        tax += (salary - 4500) * 0.28;
        salary = 4500;
    }
    if (salary > 3000)
    {
        tax += (salary - 3000) * 0.18;
        salary = 3000;
    }
    if (salary > 2000)
    {
        tax += (salary - 2000) * 0.08;
        salary = 2000;
    }
    
    if (!tax) printf("Isenton");
    else printf("R$ %.2lfn", tax);
    
	return 0;
}

• 格式化输出
  • 整型
    • %nd 占用n个字符（不足时前面补空格）
    • %-nd 占用n个字符（不足时后面补空格）
    • %0nd 占用n个字符（不足时前面补0）
  • 浮点型
    • %n.mlf 占用n个字符保留m位小数（不足时前面补空格）
    • %-n.mlf 占用n个字符保留m位小数（不足时后面补空格）
    • %0n.mlf 占用n个字符保留m位小数（不足时前面补0）

• 条件表达式（短路逻辑）
  • 与 && and
  • 或 || or
  • 非 ! not