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SOLO-009 · Killer Sudoku

EXPERT

Captive Sums

Complete the grid completely. Only one solution respects all constraints.

Materials: Pencil and gum; no commercial material.

Rules you need

The puzzle

The empty boxes are to be completed. The given numbers are fixed. The answer and proof are on another page.

Coordinates: lines from top to bottom, columns from left to right.
L / C123456789
1208131222
2182411
31617
41241621314
51513
61018
715818121714
8199
9315

Thick stroke: region. Dotted inside the cells: cage and its total. A tint on a diagonal reminds the diagonal constraint, if it applies.

Exact list of cages (coordinates and totals)
  • Cage 1: L1C1, L1C2, L1C3, L2C1; total 20.
  • Cage 2: L1C4, L1C5, L1C6; total 13.
  • Cage 3: L1C7, L1C8; total 12.
  • Cage 4: L1C9, L2C8, L2C9, L3C8; total 22.
  • Cage 5: L2C2, L3C1, L3C2, L3C3; total 18.
  • Cage 6: L2C3, L2C4, L3C4; total 24.
  • Cage 7: L2C5, L2C6, L2C7; total 11.
  • Cage 8: L3C5, L3C6, L3C7, L4C7; total 16.
  • Cage 9: L3C9, L4C9, L5C9; total 17.
  • Cage 10: L4C1, L4C2, L5C2; total 12.
  • Cage 11: L4C3, L4C4, L5C3, L5C4; total 16.
  • Cage 12: L4C5, L5C5, L5C6; total 21.
  • Cage 13: L4C6; total 3.
  • Cage 14: L4C8, L5C8, L6C8, L6C9; total 14.
  • Cage 15: L5C1, L6C1; total 15.
  • Cage 16: L5C7, L6C7; total 13.
  • Cage 17: L6C2, L6C3, L6C4; total 10.
  • Cage 18: L6C5, L6C6, L7C5; total 18.
  • Cage 19: L7C1, L7C2; total 15.
  • Cage 20: L7C3, L8C3; total 8.
  • Cage 21: L7C4, L8C4, L9C4, L9C5; total 18.
  • Cage 22: L7C6, L8C6; total 12.
  • Cage 23: L7C7, L7C8, L8C7, L8C8; total 17.
  • Cage 24: L7C9, L8C9, L9C9; total 14.
  • Cage 25: L8C1, L8C2, L9C2, L9C3; total 19.
  • Cage 26: L8C5; total 9.
  • Cage 27: L9C1; total 3.
  • Cage 28: L9C6, L9C7, L9C8; total 15.
Why this level?

After unique candidates, single places, bare pairs/triples and interactions between units, the solver still reaches bifurcations. The exhaustive proof reaches 3 intertwined hypotheses, examines 9 states and closes 4 branches by contradiction. The Expert level asks to keep a chain of possibilities in addition to the interactions. Editorial evaluation according to the protocol of the collection, without calibration on a panel of players; another logical path can be shorter.

Your workspace

Write down your assumptions separately from deductions you have proved.