将对称满阵a转化为稀疏存储：按行存储 寻找上三角阵首个非零元位置，上三角阵非零元所在列，非零元值，对角元值(Convert symmetric full array a into sparse storage: store by line Find the first nonzero element position of the upper triangular array, the nonzero element of the upper triangular array, the no