zoukankan      html  css  js  c++  java
  • POJ

    Andy the smart computer science student was attending an algorithms class when the professor asked the students a simple question, "Can you propose an efficient algorithm to find the length of the largest palindrome in a string?" 

    A string is said to be a palindrome if it reads the same both forwards and backwards, for example "madam" is a palindrome while "acm" is not. 

    The students recognized that this is a classical problem but couldn't come up with a solution better than iterating over all substrings and checking whether they are palindrome or not, obviously this algorithm is not efficient at all, after a while Andy raised his hand and said "Okay, I've a better algorithm" and before he starts to explain his idea he stopped for a moment and then said "Well, I've an even better algorithm!". 

    If you think you know Andy's final solution then prove it! Given a string of at most 1000000 characters find and print the length of the largest palindrome inside this string.

    Input

    Your program will be tested on at most 30 test cases, each test case is given as a string of at most 1000000 lowercase characters on a line by itself. The input is terminated by a line that starts with the string "END" (quotes for clarity). 

    Output

    For each test case in the input print the test case number and the length of the largest palindrome. 

    Sample Input

    abcbabcbabcba
    abacacbaaaab
    END

    Sample Output

    Case 1: 13
    Case 2: 6

    思路:求一个字符串的最长回文子串,manacher算法或者预处理前后缀hash值二分求解。我写的manacher。
     1 #include <iostream>
     2 #include <fstream>
     3 #include <sstream>
     4 #include <cstdlib>
     5 #include <cstdio>
     6 #include <cmath>
     7 #include <string>
     8 #include <cstring>
     9 #include <algorithm>
    10 #include <queue>
    11 #include <stack>
    12 #include <vector>
    13 #include <set>
    14 #include <map>
    15 #include <list>
    16 #include <iomanip>
    17 #include <cctype>
    18 #include <cassert>
    19 #include <bitset>
    20 #include <ctime>
    21 
    22 using namespace std;
    23 
    24 #define pau system("pause")
    25 #define ll long long
    26 #define pii pair<int, int>
    27 #define pb push_back
    28 #define mp make_pair
    29 #define clr(a, x) memset(a, x, sizeof(a))
    30 
    31 const double pi = acos(-1.0);
    32 const int INF = 0x3f3f3f3f;
    33 const int MOD = 1e9 + 7;
    34 const double EPS = 1e-9;
    35 
    36 /*
    37 #include <ext/pb_ds/assoc_container.hpp>
    38 #include <ext/pb_ds/tree_policy.hpp>
    39 
    40 using namespace __gnu_pbds;
    41 tree<pli, null_type, greater<pli>, rb_tree_tag, tree_order_statistics_node_update> T;
    42 */
    43 
    44 char s[1000015], t[2000015];
    45 int ls, lt, p[2000015];
    46 void get_t() {
    47     t[0] = '@';
    48     ls = strlen(s + 1);
    49     for (int i = 1; i <= ls; ++i) {
    50         t[(i << 1) - 1]  = '#';
    51         t[i << 1] = s[i];
    52     }
    53     t[ls << 1 | 1] = '#';
    54     lt = ls << 1 | 1;
    55     t[lt + 1] = 0;
    56 }
    57 int get_maxlen() {
    58     get_t();
    59     int mi = 1, mx = 1, res = 0;
    60     p[1] = 1;
    61     for (int i = 2; i <= lt; ++i) {
    62         if (i <= mx) {
    63             p[i] = min(mx - i + 1, p[2 * mi - i]);
    64         } else {
    65             p[i] = 1;
    66         }
    67         while (t[i - p[i]] == t[i + p[i]]) ++p[i];
    68         if (mx < i + p[i]) {
    69             mi = i;
    70             mx = i + p[i] - 1;
    71         }
    72         res = max(res, p[i] - 1);
    73     }
    74     return res;
    75 }
    76 int main() {
    77     for (int ca = 1; scanf("%s", s + 1) && strcmp(s + 1, "END"); ++ca) {
    78         printf("Case %d: %d
    ", ca, get_maxlen());
    79     }
    80     return 0;
    81 }
    View Code
  • 相关阅读:
    总结c#和javascript中常见的相关的"空"
    javascript从未如此流行(JavaScript has never been so popular .)
    解决ajax调用中ie的缓存问题
    《.NET框架程序设计》第5章 基元类型、引用类型与值类型
    DataTable复制到新的DataTable并筛选
    《.NET框架程序设计》第1章 .NET开发平台体系架构 读后感
    《.NET框架程序设计》第4章 类型基础 读后感
    《.NET框架程序设计》第2章 第3章 读后感
    《道德经》程序员版第四十二章
    数据库设计总结
  • 原文地址:https://www.cnblogs.com/BIGTOM/p/8876252.html
Copyright © 2011-2022 走看看