中文说明：本function用于解决prim最小生成树当决策量过于大时的空间不足问题，一般prim算法用于解决100以内的list。因此，改进算法，主要用于光度立体求解完法向以后的梯度解表面高度。用matlab实现。
English Description：
This function is used to solve the problem of insufficient space when the decision quantity of prim minimum spanning tree is too large. The general prim algorithm is used to solve the list within 100. Therefore, the improved algorithm is mainly used to solve the surface height of normal gradient solution after photometric stereo. It is realized by MATLAB.