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main2.cpp

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+#include <iostream>
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+using namespace std;
+
+void solveroot();
+void Triangleproblem();
+void judge();
+
+void solveroot()
+{
+	double der;
+	double m, n;
+	cout << "Please enter the coefficients of the equation you want to calculate in the order of a, b, c." << endl;
+	double a, b, c;
+	cin >> a;
+	cin >> b;
+	cin >> c;
+	der = b * b - 4 * a*c;
+	int boolist;
+	if (der == 0)       //表示有两个相同的根
+	{
+		boolist = 1;
+	}
+	else if (der < 0)   //表示有两个非有理数的根
+	{
+		boolist = 0;
+	}
+	else      //表示有两个不同的根
+	{
+		boolist = 2;
+	}
+	switch (boolist)
+	{
+	case 0:
+		der = -der;
+		m = (-b) / (2 * a);
+		n = sqrt(der) / (2 * a);
+		cout << "The equation has two complex roots" << endl;
+		printf("x1=%.3f+%.3fi x2=%.3f-%.3fi", m, n, m, n);
+		break;
+	case 1:
+		m = (-b) / (2 * a);
+		n = sqrt(der) / (2 * a);
+		cout << "The equation has two identical roots" << endl;
+		printf("x1=%.3f x2=%.3f", m + n, m - n);
+		break;
+	case 2:
+		m = (-b) / (2 * a);
+		n = sqrt(der) / (2 * a);
+		cout << "The equation has two different roots" << endl;
+		printf("x1=%.3f x2=%.3f", m + n, m - n);
+		break;
+	}
+}
+
+void Triangleproblem()
+{
+	double a, b, c;
+	double s;
+	double fai;
+	double number;
+	cout << "Please enter the side length of the three sides of the triangle" << endl;
+	cin >> a >> b >> c;
+	fai = (a + b + c) / 2;
+	number = fai * (fai - a)*(fai - b)*(fai - c);
+	s = sqrt(number);
+	cout << "The area of the triangle is：" << s << endl;
+}
+
+void judge()
+{
+	int year, day;
+	int sum, boolist;
+	int month;
+	cout << "Please enter today's date in the format of year-month-date" << endl;
+	cin >> year;
+	getchar();
+	cin >> month;
+	getchar();
+	cin >> day;
+	getchar();
+	switch (month)
+	{
+	case 1:sum = 0; break;
+	case 2:sum = 31; break;
+	case 3:sum = 59; break;
+	case 4:sum = 90; break;
+	case 5:sum = 120; break;
+	case 6:sum = 151; break;
+	case 7:sum = 181; break;
+	case 8:sum = 212; break;
+	case 9:sum = 243; break;
+	case 10:sum = 273; break;
+	case 11:sum = 304; break;
+	case 12:sum = 334; break;
+	default:cout << "data error" << endl; break;
+	}
+	sum = sum + day;
+
+	if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
+	{
+		boolist = 1;
+	}
+	if (boolist == 1 && month > 2)
+	{
+		sum = sum + 1;
+	}
+	cout << "As of today, this year has passed a total of " << sum << "days.";
+	int a, b;
+	a = sum / 7;
+	b = sum - a * 7;
+	cout << "The week is" << a << "and the day is" << b << endl;
+}
+
+int main()
+{
+	int w;
+	cout << "The program can complete three tasks" << endl;
+	cout << "The task one finds the root of the quadratic equation" << endl;
+	cout << "The task two knows the three sides of the triangle to find the area" << endl;
+	cout << "The task three judges today according to the date." << endl;
+	cout << "Please enter the action you want to take" << endl;
+	cin >> w;
+	switch (w)
+	{
+	case 1:solveroot(); break;
+	case 2:Triangleproblem(); break;
+	case 3:judge(); break;
+	}
+	return 0;
+}