Notes on this puzzle
Skyscrapers #5112 is a 4×4 city: every row and column holds the heights 1 to 4 once, and 12 of the 16 edge positions carry a clue. No heights are given inside the grid; the edge clues do all the work.
There is 1 clue of 1 around the frame; the first cell beside each of them must hold a 4. 1 clue shows 4: that line rises one step at a time. On 2 lines the two opposite clues add up to 5, which fixes exactly where the tallest building stands. The top edge carries the most clues (3). 4 edge positions are blank, so parts of the grid are solved from the inside out.
Where to beginTry row 1, column 2 first: its row and column clues decide it without any other help. Place the 4s next to every clue of 1, then fill each line like a tiny sudoku.