Jump Game: Minimum Jumps

/*
 * Problem : Fewest jumps.
 * Input   : The array.
 * Output  : The number of jumps.
 * Approach: Greedy ranges
 * Time    : O(n)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static long solve(int[] a) {
        // Step 1: end is the farthest index that the current number of jumps can reach. farthest is the best next reach.
        int jumps = 0;
        int end = 0;
        int farthest = 0;
        // Step 2: The last index needs no jump from itself, so the loop stops one index before it.
        for (int i = 0; i < a.length - 1; i++) {
            farthest = Math.max(farthest, i + a[i]);
            // Step 3: At the end of the current range, one more jump is needed. The new range goes to the best reach.
            if (i == end) {
                jumps++;
                end = farthest;
            }
        }
        return jumps;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = scanner.nextInt();
        }
        System.out.println(solve(a));
    }
}