代码随想录算法训练营第45天 | 198.打家劫舍 、213.打家劫舍II 、337.打家劫舍III

今天就是打家劫舍的一天，这个系列不算难，大家可以一口气拿下。

198.打家劫舍
视频讲解：https://www.bilibili.com/video/BV1Te411N7SX
https://programmercarl.com/0198.打家劫舍.html

/**
 * @param {number[]} nums
 * @return {number}
 */
var rob = function(nums) {
    const dp = new Array(nums.length);
    dp[0] = nums[0];
    dp[1] = Math.max(nums[0], nums[1]);
    for (let i=2;i<nums.length;i++) {
        dp[i] = Math.max(dp[i-2]+ nums[i], dp[i-1] );
    }

    return dp[nums.length-1];
};

213.打家劫舍II
视频讲解：https://www.bilibili.com/video/BV1oM411B7xq
https://programmercarl.com/0213.打家劫舍II.html

在一的基础上变了下
var numsDp = function(nums) {
    const dp = new Array(nums.length);
    dp[0] = nums[0];
    dp[1] = Math.max(nums[0], nums[1]);
    for (let i=2;i<nums.length;i++) {
        dp[i] = Math.max(dp[i-2]+ nums[i], dp[i-1] );
    }

    return dp[nums.length-1];
};

/**
 * @param {number[]} nums
 * @return {number}
 */
var rob = function(nums) {
    if (nums.length === 1) return nums[0]
    const nums1 = numsDp(nums.slice(0, nums.length - 1));
    const nums2 = numsDp(nums.slice(1, nums.length));
    return Math.max(nums1, nums2);
};

337.打家劫舍III
视频讲解：https://www.bilibili.com/video/BV1H24y1Q7sY
https://programmercarl.com/0337.打家劫舍III.html

树形dp
/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var rob = function(root) {
    const backtracing = (node) => {
        if (node === null) {
            return [0, 0];
        }
        let leftDp = backtracing(node.left);
        let rightDp = backtracing(node.right);

        const dp = [];
        dp[0] = Math.max(leftDp[1],leftDp[0]) + Math.max(rightDp[1],rightDp[0]);
        dp[1] = leftDp[0] + rightDp[0] + node.val;
        return dp;
    }

    const dpRoot = backtracing(root);
    return Math.max(dpRoot[0],dpRoot[1]);
};