C :

#include <stdio.h>
#include <string.h>
#define min(a,b) (a<b?a:b)
char str1[3100],str2[3100];
int dp[3100][3100];
int main()
{
    int i,j,t,len1,len2;
    while(~scanf("%s%s",str1,str2))
    {
         len1 = strlen(str1);
         len2 = strlen(str2);
        for( i=0; i<=len1; i++) dp[i][0] = i;
        for( j=0; j<=len2; j++) dp[0][j] = j;
        for( i=1; i<=len1; i++)
        {
            for( j=1; j<=len2; j++)
            {
                 t = (str1[i-1] == str2[j-1])?0:1;
                dp[i][j] = min(dp[i-1][j-1] + t, dp[i-1][j]+1);
                dp[i][j] = min(dp[i][j],dp[i][j-1]+1);
            }
        }
        printf("%d",dp[len1][len2]);
    }
    return 0;
}

C++ :

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
char str1[3100],str2[3100];
int dp[3100][3100];
int main()
{
    while(~scanf("%s%s",str1,str2))
    {
        int len1 = strlen(str1);
        int len2 = strlen(str2);
        for(int i=0; i<=len1; i++) dp[i][0] = i;
        for(int j=0; j<=len2; j++) dp[0][j] = j;
        for(int i=1; i<=len1; i++)
        {
            for(int j=1; j<=len2; j++)
            {
                int t = (str1[i-1] == str2[j-1])?0:1;
                dp[i][j] = min(dp[i-1][j-1] + t, dp[i-1][j]+1);
                dp[i][j] = min(dp[i][j],dp[i][j-1]+1);
            }
        }
        printf("%d",dp[len1][len2]);
    }
    return 0;
}

Pascal :

uses math;
var s,s1:ansistring;f:array[0..2050,0..2050]of longint;i,j:longint;
begin
  readln(s);
  readln(s1);
  for i:=1 to length(s1) do f[0,i]:=i;
  for i:=1 to length(s) do f[i,0]:=i;
  for i:=1 to length(s) do
    for j:=1 to length(s1) do
      if s[i]=s1[j] then f[i,j]:=f[i-1,j-1]
      else f[i,j]:=min(min(f[i-1,j-1]+1,f[i-1,j]+1),f[i,j-1]+1);
  writeln(f[length(s),length(s1)]);
end.