Not OP, but you don't ever have to guess and backtrack, you can always work out the next move. After playing about 100 boards several simple "rules" emerge which allow for this.
* 5, 0, 1 1 1, 2 2, 3 1 and 3 1 are immediately solved
* 4 lets you set 3 squares immediately
* 3, 2 1 and 1 2 let you set 1 square immediately
For example, a valid "advanced" rule is this: consider a line, then consider all permutations of ways to complete it given the current state of the line. If a square is filled in/crossed out in all these permutations, then it you may fill it in/cross it out.
This is an O(n!) algorithm! In practice you only have <5 permutations.
But in general, Nonogram solving, like most pen-and-paper puzzles, is NP-Complete for large enough puzzles, so even such a high-powered rule isn't guaranteed to completely solve a (large) puzzle.