freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/6a22d77ddf034bc4e35b1d56.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
6a22d77ddf034bc4e35b1d56	Challenge 349: Cell Signal	29	challenge-349

--description--

Given a grid containing three cell tower readings, determine the location of the phone.

• Each cell in the grid is either 0 (no tower) or a positive integer representing the number of cells to the phone, measured in a straight line: horizontal, vertical, or diagonal.
• Return the [row, col] of the cell that is the correct number of cells from all three towers.
• There is always exactly one solution.

--hints--

find_signal([[0, 0, 1], [0, 1, 0], [0, 0, 1]]) should return [1, 2].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(find_signal([[0, 0, 1], [0, 1, 0], [0, 0, 1]]), [1, 2])`)
}})

find_signal([[0, 2, 0], [1, 0, 0], [0, 0, 1]]) should return [2, 1].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(find_signal([[0, 2, 0], [1, 0, 0], [0, 0, 1]]), [2, 1])`)
}})

find_signal([[0, 0, 2, 0], [0, 0, 0, 0], [2, 0, 0, 0], [0, 0, 0, 1]]) should return [2, 2].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(find_signal([[0, 0, 2, 0], [0, 0, 0, 0], [2, 0, 0, 0], [0, 0, 0, 1]]), [2, 2])`)
}})

find_signal([[0, 3, 0, 0, 0], [0, 0, 0, 0, 2], [0, 0, 0, 0, 0], [4, 0, 0, 0, 0], [0, 0, 0, 0, 0]]) should return [3, 4].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(find_signal([[0, 3, 0, 0, 0], [0, 0, 0, 0, 2], [0, 0, 0, 0, 0], [4, 0, 0, 0, 0], [0, 0, 0, 0, 0]]), [3, 4])`)
}})

find_signal([[3, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 2, 0, 0, 0, 2]]) should return [3, 3].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(find_signal([[3, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0], [0, 2, 0, 0, 0, 2]]), [3, 3])`)
}})

--seed--

--seed-contents--

def find_signal(grid):

    return grid

--solutions--

def find_signal(grid):
    rows = len(grid)
    cols = len(grid[0])

    towers = []
    for r in range(rows):
        for c in range(cols):
            if grid[r][c] != 0:
                towers.append((r, c, grid[r][c]))

    def is_valid(r, c, tr, tc, dist):
        dr = abs(r - tr)
        dc = abs(c - tc)
        return (dr == dist or dc == dist) and (dr == 0 or dc == 0 or dr == dc)

    for r in range(rows):
        for c in range(cols):
            if grid[r][c] != 0:
                continue
            if all(is_valid(r, c, tr, tc, dist) for tr, tc, dist in towers):
                return [r, c]