Challenge #23: 🎁 Gift route

Santa Claus 🎅 has to deliver presents in a town represented as a grid map.

Each cell on the map can be:

• 'S' → Santa's starting point (where the presents are)
• 'G' → House that must receive a present
• '.' → Free path
• '#' → Obstacle (cannot be crossed)

Santa makes independent deliveries for each present. He leaves from 'S', delivers the present to a house 'G', and immediately returns to 'S' to pick up the next one. However, for this challenge, we only want to calculate the sum of the minimum one-way distances from 'S' to each house 'G'.

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🎯 Your goal

Write the function minStepsToDeliver(map) that returns the total number of steps required to reach all the houses with presents from the starting position.

Keep in mind:

1. You always start from the initial position 'S'.
2. For each present, you must calculate the minimum distance from 'S' to that house 'G'.
3. Obstacles ('#') cannot be crossed.
4. If any house with a present is unreachable, the function must return -1.

🧩 Examples

minStepsToDeliver([
  ['S', '.', 'G'],
  ['.', '#', '.'],
  ['G', '.', '.']
])
// Result: 4

/* 
Explanation:
- Minimum distance from S (0,0) to G (0,2): 2 steps
- Minimum distance from S (0,0) to G (2,0): 2 steps
- Total: 2 + 2 = 4
*/

minStepsToDeliver([
  ['S', '#', 'G'],
  ['#', '#', '.'],
  ['G', '.', '.']
])
// Result: -1
// (The house at (0,2) is unreachable due to obstacles)

minStepsToDeliver([['S', 'G']])
// Result: 1

🎯 Rules

• The map always contains exactly one 'S'.
• There can be zero or more houses with presents ('G').
• The order of deliveries doesn't matter, as each is measured independently from 'S'.
• You must return the sum of the minimum one-way distances.

🧠 Hint

• Calculate the shortest distance from 'S' to each 'G' (you can use a Breadth-First Search or BFS algorithm).
• If any present has no possible path, the total result is -1.