题目

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代码

#include <iostream>
#include <cmath>
#include <functional>using namespace std;// 定积分函数
double integrate(function<double(double)> func, double a, double b, int num_intervals) {double h = (b - a) / num_intervals;  // 计算每个小区间的宽度double result = (func(a) + func(b)) / 2.0;  // 初始化结果为端点的函数值之和的一半// 使用梯形法则进行数值积分for (int i = 1; i < num_intervals; ++i) {double x = a + i * h;result += func(x);}result *= h;  // 乘以小区间宽度得到最终结果return result;
}// 要积分的函数
double Func1(double x) {return x + 2 - x * x;
}
double Func2(double x) {return sqrt(1 - x * x) + x;
}
double Func3(double x) {double tmp = (4 - x * x);return sqrt(tmp * tmp * tmp);
}
double Func4(double x) {return sin(x);
}function<double(double)> ReturnFunc(int op) {if (op == 1) return Func1;else if (op == 2) return Func2;else if (op == 3) return Func3;else return Func4;
}int main() {int num_intervals = 1000;int op; double a, b;while (cin >> op >> a >> b) {auto f = ReturnFunc(op);double result = integrate(f, a, b, num_intervals);if (op != 4)printf("∫[%.2lf~%.2lf]f%d(x)dx=%.2lf\n", a, b, op, result);else {printf("∫[%.2lf~%.2lf]sin(x)dx=%.2lf\n", a, b, result);}}return 0;
}

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