C++ :

#include <iostream>
#include <cmath>
 
#define MAX 100000    //标识最大的可能整数
 
int val[300][300];
 
std::string stra;        //字符串A
std::string strb;       //字符串B
int k;        //定值k
 
//返回字符a与b的ASCII码的差的绝对值
int dist(char a, char b)
{
         return abs(a-b);     
}
 
int comp()
{
         int len1, len2;
         int tmp;
         val[0][0] = 0;
         len1 =    stra.length();
         len2 = strb.length();
        
         for(int i=0; i<=len1; i++)   //字符串A和B的有效下标是º1~len,下标0表示空字符串
         {                                                                //i或j是0表示A或B串为空串
                   for(int j=0; j<=len2; j++)
                   {
                            if(i+j)//i和j至少一个大于0
                            {
                                     val[i][j] = MAX;
                                    
                                     tmp = val[i-1][j] + k;
                                     if(i && (tmp<val[i][j]))//i大于0
                                               val[i][j] = tmp;
                                              
                                     tmp = val[i][j-1]+k;
                                     if(j && (tmp<val[i][j]))//j大于0
                                               val[i][j] = tmp;
                                              
                                     tmp = val[i-1][j-1] + dist(stra[i], strb[j]);
                                     if((i*j) && (tmp<val[i][j])) //i和j至少有一个不为0
                                               val[i][j] = tmp;                                          
                            }
                   }       
         }
         return val[len1][len2];
}
 
int main()
{
         std::cin>>stra>>strb>>k;
         stra = " " + stra;      //此处在字符串开头添加一个空格，是为了使字符串stra
         strb = " " + strb;    //的控制台输入的有效字符下标从1到stra.length()
         std::cout<<comp()<<std::endl;
        // system("pause");
         return 0;
}