Day50.算法训练

198. 打家劫舍

class Solution {
    public int rob(int[] nums) {

        if(nums.length ==1){
            return nums[0];
        }

        int[] dp = new int[nums.length];
        dp[0] = nums[0];
        dp[1] = Integer.max(nums[0], nums[1]);

        for (int i = 2; i < nums.length; i++) {
            dp[i] = Integer.max(dp[i - 1], dp[i - 2] + nums[i]);
        }
        return dp[nums.length - 1];
    }
}

213. 打家劫舍 II

class Solution {
        public int rob(int[] nums) {
            if (nums.length == 1) {
                return nums[0];
            }
            int rob1 = rob2(Arrays.copyOfRange(nums, 0, nums.length - 1));
            int rob2 = rob2(Arrays.copyOfRange(nums, 1, nums.length));
            return Integer.max(rob1, rob2);
        }

        public int rob2(int[] nums) {
            if (nums.length == 1) {
                return nums[0];
            }
            int[] dp = new int[nums.length];
            dp[0] = nums[0];
            dp[1] = Integer.max(nums[0], nums[1]);

            for (int i = 2; i < nums.length; i++) {
                dp[i] = Integer.max(dp[i - 1], dp[i - 2] + nums[i]);
            }
            return dp[nums.length - 1];
        }
    }

337. 打家劫舍 III

class Solution {
    public int rob(TreeNode root) {
        int[] ints = rob2(root);
        return Integer.max(ints[0], ints[1]);
    }

    public int[] rob2(TreeNode root) {
        if (root == null) {
            return new int[]{0, 0};
        }
        int[] leftDp = rob2(root.left);
        int[] rightDp = rob2(root.right);

        int val1 = Integer.max(leftDp[0], leftDp[1]) + Integer.max(rightDp[0], rightDp[1]);

        int val2 = root.val + leftDp[0] + rightDp[0];

        return new int[]{val1, val2};
    }
}