【leetcode】Jump Game I, II 跳跃游戏一和二

题目：

Jump Game I：

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Determine if you are able to reach the last index.

For example:
A = [2,3,1,1,4], return true.

A = [3,2,1,0,4], return false.

Jump Game II:

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Your goal is to reach the last index in the minimum number of jumps.

For example:
Given array A = [2,3,1,1,4]

The minimum number of jumps to reach the last index is 2. (Jump 1 step from index 0 to 1, then 3 steps to the last index.)

Java代码例如以下：

public class Jump_Game {

	public static void main(String[] args) {
		int[] A = { 2, 3, 1, 1, 4 };
		int[] B = { 3, 2, 1, 0, 4 };

		System.out.println(canJump(A));
		System.out.println(canJump(B));

	}

	public static boolean canJump(int[] A) {
		boolean[] can = new boolean[A.length];
		can[0] = true;

		for (int i = 1; i < A.length; i++) {
			for (int j = 0; j < i; j++) {
				if (can[j] && j + A[j] >= i) {
					can[i] = true;
					break;
				}
			}
		}
		return can[A.length - 1];
	}
}

public class jump_game_2 {

	public static void main(String[] args) {
        	int[] A = { 2, 3, 1, 1, 4 };
		int[] B = { 3, 2, 1, 0, 4 };

		System.out.println(jump(A));
		System.out.println(jump(B));
	}

	public static int jump(int[] A) {
		int[] steps = new int[A.length];
		steps[0] = 0;

		for (int i = 1; i < A.length; i++) {
			steps[i] = Integer.MAX_VALUE;
			for (int j = 0; j < i; j++) {
				if (steps[j] != Integer.MAX_VALUE && j + A[j] >= i) {
					steps[i] = steps[j] + 1;
					break;
				}
			}
		}
		return steps[A.length - 1];
	}
}