poj2752

kmp的变形，kmp算法是先将某穿和自身匹配，写出fail数组。我们只需要这个fail数组，它的最后一位存储了我们所要求的答案中的最大长度。然后每次利用fail数组向前跳转就可以得到所有答案。

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      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstdio
    
      >
    
      
#include 
    
      <
    
      cstdlib
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      
#include 
    
      <
    
      stack
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 400005
    
      


    
      char
    
       s[maxn];

    
      int
    
       fail[maxn];


    
      void
    
       kmp(
    
      char
    
      *
    
       pat)
{
 
    
      int
    
       i, k;

 memset(fail, 
    
      -
    
      1
    
      , 
    
      sizeof
    
      (fail));
 
    
      for
    
       (i 
    
      =
    
       
    
      1
    
      ; pat[i]; 
    
      ++
    
      i)
 {
 
    
      for
    
       (k
    
      =
    
      fail[i
    
      -
    
      1
    
      ]; k
    
      >=
    
      0
    
       
    
      &&
    
       pat[i]
    
      !=
    
      pat[k
    
      +
    
      1
    
      ];
 k
    
      =
    
      fail[k]);
 
    
      if
    
       (pat[k 
    
      +
    
       
    
      1
    
      ] 
    
      ==
    
       pat[i]) fail[i] 
    
      =
    
       k 
    
      +
    
       
    
      1
    
      ;
 }
}


    
      int
    
       main()
{
 
    
      //
    
      freopen("D:\\t.txt", "r", stdin);
    
      

    
       
    
      while
    
       (scanf(
    
      "
    
      %s
    
      "
    
      , s) 
    
      !=
    
       EOF)
 {
 kmp(s);
 
    
      int
    
       temp 
    
      =
    
       strlen(s) 
    
      -
    
       
    
      1
    
      ;
 stack 
    
      <
    
      int
    
      >
    
       stk;
 
    
      while
    
       (temp 
    
      !=
    
       
    
      -
    
      1
    
      )
 {
 stk.push(temp 
    
      +
    
       
    
      1
    
      );
 temp 
    
      =
    
       fail[temp];
 }
 printf(
    
      "
    
      %d
    
      "
    
      , stk.top());
 stk.pop();
 
    
      while
    
       (
    
      !
    
      stk.empty())
 {
 printf(
    
      "
    
       %d
    
      "
    
      , stk.top());
 stk.pop();
 }
 printf(
    
      "
    
      \n
    
      "
    
      );
 }
 
    
      return
    
       
    
      0
    
      ;
}