第21天--算法（Leetcode 687）
687.最长同值路径
public int longestUnivaluePath(TreeNode root) { if(root == null) { return 0; } return process(root).notBeginX - 1; } public Info process(TreeNode root) { if(root == null) { return new Info(0,0); } TreeNode l = root.left; TreeNode r = root.right; Info left = process(l); Info right = process(r); int beginX; int notBeginX; beginX = 1; if(l != null) { if(root.val == l.val) { beginX = 1 + left.beginX; } } if(r != null) { if(root.val == r.val) { beginX = Math.max(1 + right.beginX,beginX); } } notBeginX = Math.max(beginX,Math.max(left.notBeginX,right.notBeginX)); if(l != null && r != null && root.val == l.val && root.val == r.val) { notBeginX = Math.max(notBeginX,left.beginX + right.beginX + 1); } return new Info(beginX,notBeginX); } class Info { int beginX; int notBeginX; public Info(int beginX,int notBeginX) { this.beginX = beginX; this.notBeginX = notBeginX; } }