HDU 1544 Palindromes(回文字符子串)
阿新 • • 發佈:2017-11-30
mar length bre tput for ons 文字 rom pre
Input
There are several test cases in the input. Each case contains a non-empty string which has no more than 5000 characters.
A regular palindrome is a string of numbers or letters that is the same forward as backward. For example, the string "ABCDEDCBA" is a palindrome because it is the same when the string is read from left to right as when the string is read from right to left.
Now give you a string S, you should count how many palindromes in any consecutive substring of S.
There are several test cases in the input. Each case contains a non-empty string which has no more than 5000 characters.
Proceed to the end of file.
Output
A single line with the number of palindrome substrings for each case.
Sample Input
aba
aa
Sample Output
4
3
題意:
問有多少個回文的子串。
題解:
從子串的長度考慮,長度為奇數的子串:它的中心只能在[1,len-2]範圍內,分別從中心開始向兩邊擴展,遇到不回文就直接停止拓展。長度為偶數的子串:中心對稱的左數範圍在[0,len-2],分別以這中心的兩個數向兩邊擴展。
#include<iostream> #include<string> #include<algorithm> using namespace std; int main() { string s; while(cin>>s) { int ans=0; int len=s.length(); for(int i=1;i<len-1;i++) { for(int j=1;i-j>=0&&i+j<len;j++) { if(s[i-j]==s[i+j]) ans++; else break; } } for(int i=0;i<len-1;i++) { for(int j=0;i-j>=0&&i+j+1<len;j++) { if(s[i-j]==s[i+j+1]) ans++; else break; } } cout<<ans+len<<endl; } return 0; }
HDU 1544 Palindromes(回文字符子串)