第三题用的递归写的。已AC。 public class NCLongestSingleColorPath { public int max=0; public int findPath(TreeNode root) { // write code here recur(root); return max; } public int[] recur(TreeNode root){ int[] res = new int[]{0,0}; if(root==null) return res; int[] left = recur(root.left); int[] right = recur(root.right); res[root.val]=Math.max(left[root.val],right[root.val])+1; int temp=left[root.val]+right[root.val]+1; if(temp>max) max = temp; return res; } }