poj2782

简单题，先从大到小排序，然后从两端开始向中间看看能不能把右端的匹配给左端。

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

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 100005
    
      


    
      int
    
       n, m;

    
      int
    
       f[maxn];


    
      int
    
       cmp(
    
      int
    
       a, 
    
      int
    
       b)
{
 
    
      return
    
       a 
    
      >
    
       b;
}


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

    
       scanf(
    
      "
    
      %d%d
    
      "
    
      , 
    
      &
    
      n, 
    
      &
    
      m);
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      f[i]);
 sort(f, f 
    
      +
    
       n, cmp);
 
    
      int
    
       l 
    
      =
    
       
    
      0
    
      , r 
    
      =
    
       n 
    
      -
    
       
    
      1
    
      ;
 
    
      while
    
       (l 
    
      <=
    
       r)
 {
 
    
      if
    
       (f[l] 
    
      +
    
       f[r] 
    
      <=
    
       m)
 r
    
      --
    
      ;
 l
    
      ++
    
      ;
 }
 printf(
    
      "
    
      %d\n
    
      "
    
      , l);
 
    
      return
    
       
    
      0
    
      ;
}