leetcode——124. 二叉树中的最大路径和

Posted 2020-12-12 欣姐姐

 

 动态规划好巧妙啊啊啊啊啊啊啊 啊

int max =Integer.MIN_VALUE;
    public int maxPathSum(TreeNode root) {
        //用动态规划来求解
        //DFS
        //根节点的值、左子树的值、右子树的值、
        dfs(root);
        return max;
    }

    private int dfs(TreeNode node) {
        if(node == null){
            return 0;
        }
        int left = dfs(node.left);
        int right = dfs(node.right);
        int sum = node.val;
        if(left > 0) sum +=left;
        if(right > 0) sum += right;
        max = Math.max(max,sum);
        return Math.max(left,right)>0?Math.max(left,right)+node.val:node.val;
    }

 

 

——2020.6.24