Rt，spj求最优解的DP是假算法。
正确的是 fi,j=min{mink<i{fk,j+Ak,i},mink<j{fi,k+Ak,j}}f_{i,j} = \min\{\min\limits_{k< i}\{f_{k,j}+A_{k,i}\}, \min\limits_{k< j}\{f_{i,k}+A_{k,j}\}\}fi,j=min{k<imin{fk,j+Ak,i},k<jmin{fi,k+Ak,j}}
