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#include <iostream>
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#include <string>
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using std::cout, std::string, std::endl;
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class Integrate
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{
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protected:
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double a, b;
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int n;
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public:
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virtual double fun(double x) = 0;
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Integrate(double _a, double _b, int _n = 10000) : a{_a}, b{_b}, n{_n} {}
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double integrate()
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{
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double result{(fun(a) + fun(b)) / 2};
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double h{(b - a) / n};
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for (int i{1}; i < n; i++)
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result += fun(a + i * h);
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result *= h;
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return result;
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}
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};
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class F1 : public Integrate
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{
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public:
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using Integrate::Integrate;
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double fun(double x) override
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{
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return x;
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}
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};
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class F2 : public Integrate
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{
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public:
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using Integrate::Integrate;
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double fun(double x) override
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{
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return x * x;
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}
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};
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class F3 : public Integrate
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{
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public:
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using Integrate::Integrate;
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double fun(double x) override
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{
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return x * x * x;
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}
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};
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int compare(Integrate &a, Integrate &b)
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{
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// 比较两个积分对象值的结果，a大返回1，b大返回-1，相同返回0
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if (a.integrate() > b.integrate())
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return 1;
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if (a.integrate() < b.integrate())
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return -1;
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return 0;
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}
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int main()
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{
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F1 f1{0, 1};
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F2 f2{0, 1};
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F3 f3{0, 1};
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cout << f1.integrate() << ' ' << f2.integrate() << ' ' << f3.integrate() << '\n';
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// 设计通用接口compare，积分类的任意派生对象可进行比较
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cout << compare(f1, f2) << '\n';
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cout << compare(f1, f3) << '\n';
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cout << compare(f2, f3) << '\n';
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} |
