四种方法求积分：runge-kutta法，crank_nicolson法，adams法，ab4-am4法，改进型ab4-am4法-four methods for ranking : Runge - Kutta method, crank_nicolson, adams, ab4 - am4, improved ab4 - am4 France

ACM经典程序设计源代码:高斯算法1,消元法,龙格库塔方法-ACM classical programming source code: Gaussian Algorithm 1, elimination method, Runge-Kutta methods