oko

Your mission

Confirm a launch only when the same sector lights up on two scans in a row.

today's brief

September 26, 1983. Just after midnight, the Soviet early warning system tells Stanislav Petrov that the United States has launched. Five missiles, one after another, and his job that night was to pass it straight up the chain. He called it a false alarm instead, reasoning that a real first strike would not arrive in fives. Sunlight off high cloud had lined up with the satellite sensors. Confirm a track only when it holds.

See it in action

confirm({0,1,0,0, 0,1,0,0}, 2, 4)

Expected result

Your checklist

For your own tracking. Tests grade your code.

grid holds scans rows of sectors values, one row after another. grid[r * sectors + c] is 1 when sector c lit up on scan r, and 0 when it did not.
A launch is confirmed when a sector is lit on two scans in a row.
Return the sector of the first confirmation: the earliest pair of scans, then the leftmost sector.
Return -1 when nothing is confirmed.

More examples

confirm({1,0,0,0, 0,0,0,0, 0,0,0,0}, 3, 4)

Expected result

-1

confirm({1,1, 1,1}, 2, 2)

Expected result

Constraints

Expected files

oko.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

oko

Your mission

Confirm a launch only when the same sector lights up on two scans in a row.

today's brief

See it in action

confirm({0,1,0,0, 0,1,0,0}, 2, 4)

Expected result

Your checklist

For your own tracking. Tests grade your code.

grid holds scans rows of sectors values, one row after another. grid[r * sectors + c] is 1 when sector c lit up on scan r, and 0 when it did not.
A launch is confirmed when a sector is lit on two scans in a row.
Return the sector of the first confirmation: the earliest pair of scans, then the leftmost sector.
Return -1 when nothing is confirmed.

More examples

confirm({1,0,0,0, 0,0,0,0, 0,0,0,0}, 3, 4)

Expected result

-1

confirm({1,1, 1,1}, 2, 2)

Expected result

Constraints

Expected files

oko.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions