用 C++ 表示 N 为和所需的回文数最小数量。
问题陈述
给定一个数字 N,我们必须找出表示 N 为它们的和所需的最小回文数数量
如果 N = 15,则需要 2 个回文数,即 8 和 7。
算法
1. Generate all the palindromes up to N in a sorted fashion 2. Find the size of the smallest subset such that its sum is N
示例
#include <iostream> #include <vector> #include <climits> #include <algorithm> using namespace std; vector<vector<long long>> table; int createPalindrome(int input, bool isOdd){ int n = input; int palindrome = input; if (isOdd) n /= 10; while (n > 0) { palindrome = palindrome * 10 + (n % 10); n /= 10; } return palindrome; } vector<int>generatePalindromes(int n){ vector<int> palindromes; int number; for (int j = 0; j < 2; j++) { int i = 1; while ((number = createPalindrome(i++, j)) <= n) palindromes.push_back(number); } return palindromes; } long long minSubsetSize(vector<int>& vec, int i, int j, int n){ if (n == 0) return 0; if (i > j || vec[i] > n) return INT_MAX; if (table[i][n]) return table[i][n]; table[i][n] = min(1 + minSubsetSize(vec, i + 1, j, n - vec[i]), minSubsetSize(vec, i + 1, j, n)); return table[i][n]; } int requiredPalindromes(int n){ vector<int> palindromes = generatePalindromes(n); sort(palindromes.begin(), palindromes.end()); table = vector<vector<long long>>(palindromes.size(), vector<long long>(n + 1, 0)); return minSubsetSize(palindromes, 0, palindromes.size() - 1, n); } int main(){ int n = 15; cout << "Minimum required palindromes = " << requiredPalindromes(n) << endl; return 0; }
输出
编译并执行以上程序时。它将生成以下输出 −
Minimum required palindromes = 2
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