说白了就是化简为类似斜对角的向量组.所以对矩阵做线性变换.
|1,0,1,1|
|1,1,1,-1|->
|1,2,3,1|
|1,0,1,1|
|0,1,0,-2|->
|0,2,2,0|
|1,0,1,1|
|0,1,0,-2|->
|0,0,2,4|
|1,0,1,1|
|0,1,0,-2|->
|0,0,1,2|
|1,0,0,-1|
|0,1,0,-2| 就是所求
|0,0,1,2|