Jump Game II - Algorithm

Think of it as BFS. Level $0$ is index $0$. Level $1$ is all indices reachable in $1$ jump. And so on. Track:

• currentEnd: the furthest index reachable with current number of jumps: furthest: the furthest index reachable with one more jump: jumps: number of jumps made When you reach currentEnd, you must jump. Update currentEnd = furthest and increment jumps. Time: $O(n)$. Space: $O(1)$. Without this level-based view, you would try all jump sequences in exponential time.