answer:Here is a Python solution to generate permutations using a backtracking algorithm in lexicographic order: ```python def permute(s): s = sorted(s) # sort the string to get lexicographic order result = [] backtrack(result, [], s) return result def backtrack(result, current, remaining): if not remaining: result.append(''.join(current)) for i in range(len(remaining)): current.append(remaining[i]) backtrack(result, current, remaining[:i] + remaining[i+1:]) current.pop() # backtrack def main(): s = abc permutations = permute(s) for perm in permutations: print(perm) if __name__ == __main__: main() ``` However, the above approach still requires sorting the output to achieve lexicographic order when duplicates exist in the string. Here is an advanced version of the algorithm where the permutations are generated in lexicographic order without the need to sort the final output. ```python def permute(s): s = sorted(s) # sort the string to get lexicographic order result = [] used = [False]*len(s) backtrack(result, [], s, used) return result def backtrack(result, current, s, used): if len(current) == len(s): result.append(''.join(current)) for i in range(len(s)): if used[i] or (i > 0 and s[i] == s[i-1] and not used[i-1]): continue used[i] = True current.append(s[i]) backtrack(result, current, s, used) used[i] = False current.pop() # backtrack def main(): s = abc permutations = permute(s) for perm in permutations: print(perm) if __name__ == __main__: main() ``` This version skips duplicate permutations by checking if the current character is equal to the previous one and if the previous one has not been used yet. If this condition is true, it skips the current character to avoid duplicate permutations.

answer:Here is the C++ code that generates all permutations of the characters of an input string using a backtracking algorithm in lexicographic order: ```cpp #include <iostream> #include <algorithm> #include <string> using namespace std; void backtrack(string& s, int start, int end) { if (start == end) { cout << s << endl; } for (int i = start; i <= end; i++) { swap(s[start], s[i]); backtrack(s, start + 1, end); swap(s[start], s[i]); // backtrack } } void permute(string s) { sort(s.begin(), s.end()); // sort the string to get lexicographic order backtrack(s, 0, s.length() - 1); } int main() { string s = abc; permute(s); return 0; } ``` However, the above approach still requires sorting the output to achieve lexicographic order when duplicates exist in the string. Here is an advanced version of the algorithm where the permutations are generated in lexicographic order without the need to sort the final output. ```cpp #include <iostream> #include <algorithm> #include <string> using namespace std; void backtrack(string& s, int start, int end, bool* used) { if (start == end) { cout << s << endl; } for (int i = start; i <= end; i++) { if (used[i] || (i > start && s[i] == s[i-1] && !used[i-1])) { continue; } swap(s[start], s[i]); used[i] = true; backtrack(s, start + 1, end, used); used[i] = false; swap(s[start], s[i]); // backtrack } } void permute(string s) { sort(s.begin(), s.end()); // sort the string to get lexicographic order bool used[s.length()] = {false}; backtrack(s, 0, s.length() - 1, used); } int main() { string s = abc; permute(s); return 0; } ``` This version skips duplicate permutations by checking if the current character is equal to the previous one and if the previous one has not been used yet. If this condition is true, it skips the current character to avoid duplicate permutations.

answer:A Canadian Forces helicopter crew successfully rescued a crane operator trapped by a fire in Kingston, Ontario, on Tuesday. The operator, initially terrified and clinging to the tip of the crane to escape the smoke and flames, was eventually secured by a rescue specialist and hoisted to safety. Capt. David Agnew, the rescue helicopter commander, noted the crew's concern about the crane collapsing. The crane operator sustained only minor injuries. The fire, which destroyed a student residence hall under construction at Queen's University, prompted the evacuation of a two-block area. Engineers remain concerned about the stability of the crane, which is still standing.

answer:Let's imagine a magical pet that brings a smile to everyone's face. How about a creature that's a cross between a rabbit and a cloud? This fluffy being, which we can call a Flumplen, has the soft, cuddly body of a rabbit but is made entirely out of wispy, white clouds. It has big, shiny eyes that change color depending on its mood and can float around, leaving a trail of sparkles wherever it goes. The Flumplen loves to play hide-and-seek among the clouds, and its favorite game is to transform into a big, puffy cloud and then suddenly pop back into its rabbit-like form, surprising its owner with a joyful Boo! It has the magical ability to make anyone who hugs it feel instantly happy and relaxed, making it the perfect pet for people who need a little stress relief. Alternatively, we could create a magical pet that's inspired by the natural world. Imagine a tiny, mischievous creature that's a combination of a dragonfly and a fairy. This Glimmerwings has iridescent wings that reflect the colors of the rainbow and can fly around its owner's head, creating a dazzling display of light and color. The Glimmerwings has the ability to grant its owner temporary glimpses into the future, but only in a playful, cryptic way. For example, it might leave a trail of glitter that spells out a mysterious message or create a miniature whirlwind that blows away a piece of paper with a hidden message. Its owner has to decipher the clues to figure out what the Glimmerwings is trying to say. Another idea could be a magical pet that's inspired by the world of music. Let's imagine a creature that's a cross between a fox and a musical instrument, like a lyre or a harp. This Melodokit has a beautiful, melodious voice and can play enchanting music on its instrument-like body. The Melodokit has the magical ability to sense its owner's emotions and play music that matches their mood. If its owner is feeling sad, the Melodokit will play a soothing lullaby; if they're feeling energetic, it will play an upbeat dance tune. Its music has the power to heal emotional wounds and bring people together, making it a beloved companion for anyone who loves music. Which of these ideas sparks your imagination?