You can use recursion. We swap the left and right child of a node, in-place, and then do the same for its children: static void reverseTree(final TreeNode root) { final TreeNode temp = root.right; root.right = root.left; root.left = temp; if (root.left != null) { reverseTree(root.left); } if (root.right != null) { reverseTree(root.right); } } … Read more
The following works with your input: d = [(‘B’, 3), (‘A’, 2), (‘A’, 1), (‘I’, 1), (‘J’, 1)] sorted(d,key=lambda x:(-x[1],x[0])) Since your “values” are numeric, you can easily reverse the sort order by changing the sign. In other words, this sort puts things in order by value (-x[1]) (the negative sign puts big numbers first) … Read more
This should do the trick. This will iterate through each word in the source string, reverse it using StringBuilder‘s built-in reverse() method, and output the reversed word. String source = “Hello World”; for (String part : source.split(” “)) { System.out.print(new StringBuilder(part).reverse().toString()); System.out.print(” “); } Output: olleH dlroW Notes: Commenters have correctly pointed out a few … Read more
Building an url with query string by string concatenation as suggested by some answers is as bad idea as building SQL queries by string concatenation. It is complicated, unelegant and especially dangerous with a user provided (untrusted) input. Unfortunately Django does not offer an easy possibility to pass query parameters to the reverse function. Python … Read more
Looking at std::reverse_iterator‘s libstdc++ implementation reveals something interesting: /** * @return A reference to the value at @c –current * * This requires that @c –current is dereferenceable. * * @warning This implementation requires that for an iterator of the * underlying iterator type, @c x, a reference obtained by * @c *x remains valid … Read more
>>> tmp = “a,b,cde” >>> tmp2 = tmp.split(‘,’) >>> tmp2.reverse() >>> “”.join(tmp2) ‘cdeba’ or simpler: >>> tmp = “a,b,cde” >>> ”.join(tmp.split(‘,’)[::-1]) ‘cdeba’ The important parts here are the split function and the join function. To reverse the list you can use reverse(), which reverses the list in place or the slicing syntax [::-1] which returns … Read more
A concise way to do this is: “”.join(reversed([a[i:i+2] for i in range(0, len(a), 2)])) This works by first breaking the string into pairs: >>> [a[i:i+2] for i in range(0, len(a), 2)] [‘AB’, ‘CD’, ‘EF’, ‘GH’] then reversing that, and finally concatenating the result back together.
The question is not well defined. Reversing arbitrary strings does not make sense and will lead to broken output. The first (surmountable) obstacle is Utf-16. Dart strings are encoded as Utf-16 and reversing just the code-units leads to invalid strings: var input = “Music \u{1d11e} for the win”; // Music 𝄞 for the win print(input.split(”).reversed.join()); … Read more
You can also do it with recursion: def reverse(text): if len(text) <= 1: return text return reverse(text[1:]) + text[0] And a simple example for the string hello: reverse(hello) = reverse(ello) + h # The recursive step = reverse(llo) + e + h = reverse(lo) + l + e + h = reverse(o) + l + … Read more