数值计算第二章编程作业：高斯顺序消元法、列选主元、三角分解法（Doolittle分解、Crout 分解）、全选主元、平方根法、追赶法解线性方程组-Order Gaussian elimination method, column pivoting, triangular decomposition (Doolittle, decomposition, decomposition Crout s), Select the main element, the square root of the