Di[r][c] if cost of travel from r to c,
         ALLOWED to visit any node numbered < i on the way

D0 = { { 0,   3,   inf,   5 },
       { 2,   0,   inf,   4 },
       { inf, 1,     0, inf },
       { inf, inf,   2,   0 } }

D1 = { { 0,   3,   inf,   5 },
       { 2,   0,   inf,   4 },
       { inf, 1,     0, inf },
       { inf, inf,   2,   0 } }

D2 = { { 0,   3,   inf,   5 },
       { 2,   0,   inf,   4 },
       { 3,   1,     0,   5 },
       { inf, inf,   2,   0 } }


D3 = { { 0,   3,   inf,   5 },
       { 2,   0,   inf,   4 },
       { 3,   1,     0,   5 },
       { 5,   3,     2,   0 } }

D4 = { { 0,   3,     7,   5 },
       { 2,   0,     6,   4 },
       { 3,   1,     0,   5 },
       { 5,   3,     2,   0 } }

 D4 shows min cost travel from anywhere to anywhere

Floyd-Warshall big-O = O(N^3)