chore: import upstream snapshot with attribution

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

@@ -0,0 +1,97 @@
+---
+id: 6a22d77ddf034bc4e35b1d56
+title: "Challenge 349: Cell Signal"
+challengeType: 29
+dashedName: 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]`.
+
+```js
+({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]`.
+
+```js
+({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]`.
+
+```js
+({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]`.
+
+```js
+({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]`.
+
+```js
+({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--
+
+```py
+def find_signal(grid):
+
+    return grid
+```
+
+# --solutions--
+
+```py
+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]
+```