In the thesis we present the 3-coloring problem of planar graphs without cycles of lengths between 4 and 9. Salavatipour (The Discharging Method in Practice, 2006) has proven that such graphs are 3-colorable and his proof can be directly rewritten as a quadratic-time algorithm. We present the discharging method which is the cornerstone for this algorithm. What is more, we focus on the time-critical part and with a careful analysis show that it is indeed not needed. Thus we invent a linear time 3-coloring algorithm of such graphs and we also evaluate its implementation.