/* its's simple. Write a program that returns the next largest number that can be created from the same digits as the input. Examples next_number(19) ➞ 91 next_number(3542) ➞ 4235 next_number(5432) ➞ 5432 next_number(58943) ➞ 59348 Notes If no larger number can be formed, return the number itself. Bonus: See if you can do this without generating all digit permutations. https://www.nayuki.io/page/next-lexicographical-permutation-algorithm next lexicographic permutation algorithm Input : enter a positive number or press submit for default value 58943 https://www.sololearn.com/post/184884/?ref=app */ #include #include #include using namespace std; auto next_largest(string const& in) { string num{in}; size_t idx{num.size()-1}, j{idx}; // find the largest index idx such that // arr[idx-1] < arr[idx] while(num.at(idx-1) >= num.at(idx)) if(! --idx) return num; // find the largest index j such that j>=idx // and arr[j] > arr[idx-1] while(j>idx && num.at(j)<=num.at(idx-1)) j--; // swap chars at index arr[idx-1] and arr[j] swap(num.at(idx-1), num.at(j)); // reverse the string starting at arr[idx] // till end reverse(begin(num)+idx, end(num)); return num; } int main() { string num{"58943"}; cin >> num; if(num.at(0) == '-' || num.at(0) == '0'){ cout << "invalid number entered - using default value as 58943\n"; num = "58943"; } for(auto&& n:vector{num, "678", "19", "543","8976", "8889"}) { cout << "original number = " << n << '\n'; cout << "next largest = " << next_largest(n) << "\n\n"; } }

[Challenge] Next_Largest_Number.cpp