00018.q

// 18. Maximum path sum I

/build layers
layers:()
layers,:enlist enlist 75
layers,:enlist 95 64
layers,:enlist 17 47 82
layers,:enlist 18 35 87 10
layers,:enlist 20 04 82 47 65
layers,:enlist 19 01 23 75 03 34
layers,:enlist 88 02 77 73 07 63 67
layers,:enlist 99 65 04 28 06 16 70 92
layers,:enlist 41 41 26 56 83 40 80 70 33
layers,:enlist 41 48 72 33 47 32 37 16 94 29
layers,:enlist 53 71 44 65 25 43 91 52 97 51 14
layers,:enlist 70 11 33 28 77 73 17 78 39 68 17 57
layers,:enlist 91 71 52 38 17 14 91 43 58 50 27 29 48
layers,:enlist 63 66 04 68 89 53 67 30 73 16 69 87 40 31
layers,:enlist 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23

/build recursive function
r:{[LAYER;OPTION;SUM]
  $[null first layers[LAYER];
    SUM;
    max .z.s[LAYER+1;OPTION;SUM+layers[LAYER;OPTION]],.z.s[LAYER+1;OPTION+1;SUM+layers[LAYER;OPTION]]
  ]
  };

/run starting from zero
r[0;0;0]
/ 1074