var minDiffInBST = function(root) { var min = Infinity var pre = null var dfs = function (root) { if (!root) return if (root.left) { dfs(root.left) } if (pre == null) { pre = root.val } else { console.log(pre,root.val) var reduce = Math.abs(pre - root.val) min = Math.min(min,reduce) pre = root.val } if (root.right) { dfs(root.right) } } dfs(root) return min };