以下是代码,请ACMER指点!
#include<iostream.h>
#include<string.h>
#include<math.h>

int p[101][101];
int t[101][101];
char str[101];
char q[101];

void back(int i,int j)//构造最优解
{while(1)
{if(i==j)
  {if(str[i]=='(')
		 q[i]=')';
	 else if(str[i]==')')
		 q[i]='(';
	 else if(str[i]=='[')
		 q[i]=']';
	 else
		 q[i]='[';
	return;
  }
 if(t[i][j]==0)
 {i=i+1;
  j=j-1;
 }
 else if(t[i][j]==1)
 {   if(str[i]=='(')
		 q[i]=')';
	 else if(str[i]==')')
		 q[i]='(';
	 else if(str[i]=='[')
		 q[i]=']';
	 else
		 q[i]='[';
	 i=i+1;
 }
 else
 {if(str[j]=='(')
		 q[j]=')';
  else if(str[i]==')')
		 q[j]='(';
  else if(str[i]=='[')
		 q[j]=']';
  else
		 q[j]='[';
  j=j-1;
 }
}
}

void main()
{int i,j,m,k;
 cin>>str;
  m=strlen(str);
  memset(p,0,sizeof(p));
  memset(t,-2,sizeof(t));
   for(i=0;i<101;i++)
	   q[i]='*';
    for(i=0;i<m;i++)
	  p[i][i]=1;
      for(k=1;k<m;k++)
	  for(i=0;i<m-k;i++)//求最优解
	  {j=i+k;
	     if(fabs(str[i]-str[j])==1||fabs(str[i]-str[j])==2)//如果str[i]与str[j]配对
		       {p[i][j]=p[i+1][j-1];
		        t[i][j]=0;
               }
		else
		{if(p[i][j-1]>p[i+1][j])
		 {p[i][j]=p[i+1][j]+1;
		     t[i][j]=1;
		 }
		  else
		  {p[i][j]=p[i][j-1]+1;
		   t[i][j]=-1;
		  }
		}
	  }
	  back(0,m-1);
	  for(i=0;i<m;i++)
	  if(q[i]=='*')
	     cout<<str[i];
	  else
	  {  if(q[i]==')'||q[i]==']')
	        cout<<str[i]<<q[i];
	     else
			cout<<q[i]<<str[i];
	  }
	  cout<<endl;
}