PAT1136:A Delayed Palindrome
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1136. A Delayed Palindrome (20)
Consider a positive integer N written in standard notation with k+1 digits ai as ak...a1a0 with 0 <= ai < 10 for all i and ak > 0. Then N is palindromic if and only if ai = ak-i for all i. Zero is written 0 and is also palindromic by definition.
Non-palindromic numbers can be paired with palindromic ones via a series of operations. First, the non-palindromic number is reversed and the result is added to the original number. If the result is not a palindromic number, this is repeated until it gives a palindromic number. Such number is called a delayed palindrome. (Quoted from https://en.wikipedia.org/wiki/Palindromic_number)
Given any positive integer, you are supposed to find its paired palindromic number.
Input Specification:
Each input file contains one test case which gives a positive integer no more than 1000 digits.
Output Specification:
For each test case, print line by line the process of finding the palindromic number. The format of each line is the following:
A + B = C
where A is the original number, B is the reversed A, and C is their sum. A starts being the input number, and this process ends until C becomes a palindromic number -- in this case we print in the last line "C is a palindromic number."; or if a palindromic number cannot be found in 10 iterations, print "Not found in 10 iterations." instead.
Sample Input 1:97152Sample Output 1:
97152 + 25179 = 122331 122331 + 133221 = 255552 255552 is a palindromic number.Sample Input 2:
196Sample Output 2:
196 + 691 = 887 887 + 788 = 1675 1675 + 5761 = 7436 7436 + 6347 = 13783 13783 + 38731 = 52514 52514 + 41525 = 94039 94039 + 93049 = 187088 187088 + 880781 = 1067869 1067869 + 9687601 = 10755470 10755470 + 07455701 = 18211171 Not found in 10 iterations.
思路
和 Pat1024 一样的题目,字符串处理问题。
代码
#include<iostream> #include<algorithm> using namespace std; bool isPalindrome(const string& s) { for(int i = 0,j = s.size() - 1;i <= j;i++,j--) { if(s[i] != s[j]) return false; } return true; } string add(const string& a,const string& b) { string tmp; int len = a.size(); int carry = 0; for(int i = len - 1;i >= 0;i--) { int cur = (a[i] - \'0\') + (b[i] - \'0\') + carry; carry = cur / 10; cur = cur % 10; tmp += (to_string(cur)); } reverse(tmp.begin(),tmp.end()); if(carry > 0) tmp.insert(0,"1"); return tmp; } int main() { string a; while(cin >> a) { int cnt = 0; while(!isPalindrome(a) && ++cnt <= 10) { string b = a; reverse(b.begin(),b.end()); string c = add(a,b); cout << a << " + " << b << " = " << c << endl; a = c; } if(cnt == 11) cout << "Not found in 10 iterations." << endl; else cout << a << " is a palindromic number." << endl; } }
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