Go: package main

import (
	"fmt"
	"os"
	"strconv"
	"bufio"
	"strings"
	"sort"
)

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				} else {
					dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				}
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: //#include "aizu.h"
#include <iostream>
#include <string>
#include <vector>

//namespace alds1_10_c{
template<class T>
T myMin(const T& arg){
	return arg;
}
template<class F, class... S>
F myMin(const F& first, const S&... second){
	F m = myMin(second...);
	if (m > first){
		return first;
	}else{
		return m;
	}
}
int f(std::string::iterator str1, const std::string& str2, const std::vector<int>& vec){
	std::vector<int> new_v;
	new_v.push_back(vec[0] + 1);
	{
		auto v = vec.begin() + 1;
		for (auto i = str2.begin(); i != str2.end(); ++i, ++v){
			if (*i == *str1){
				new_v.push_back(myMin(*v, *(v - 1), new_v.back()));
			}else{
				new_v.push_back(myMin(*v + 1, new_v.back() + 1));
			}
		}
	}
	if (*(++str1) != '\0'){
		return f(str1, str2, new_v);
	}else{
		return new_v.back();
	}
}
int main(){
	int n;
	std::cin >> n;
	for (int i = 0; i < n; ++i){
		std::string str1, str2;
		std::cin >> str1 >> str2;
		std::vector<int> vec;
    vec.push_back(0);
		for (int j = 0; j < str2.size(); ++j){
			vec.push_back(j);
		}
		std::cout << (str1.size() + str2.size() - f(str1.begin(), str2, vec)) / 2 << "\n";
	}
}
//}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#define NIL -1
using namespace std;

int count(const string& X, int i, const string Y, int j,
          vector<vector<int> >& MEMO){
    if (i >= X.size() || j >= Y.size()) return 0;
    if (MEMO[i][j] != NIL) return MEMO[i][j];
    int j_tmp = j;
    int saiyou = 0;
    while (j_tmp < Y.size()) {
        if (X[i] == Y[j_tmp]) {
            saiyou = count(X, i + 1, Y, j_tmp + 1, MEMO) + 1;
            break;
        };
        j_tmp++;
    }
    int next_X = count(X, i + 1, Y, j    , MEMO);
    // int next_Y = count(X, i    , Y, j + 1, MEMO);
    return MEMO[i][j] = max(saiyou, next_X);
}

int main(){
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        string X, Y;
        cin >> X >> Y;
        vector<vector<int> > MEMO(X.size(), vector<int>(Y.size(), NIL));
        cout << count(X, 0, Y, 0, MEMO) << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<string>
using namespace std;
string x,y;
int dp[1005][1005];
int lcs(string x,string y)
{

    int Max=-1;
    int n=x.size(),m=y.size();
    x=' '+x;
    y=' '+y;
    for(int i=1;i<=n;i++)dp[i][0]=0;        //边界条件就是从此开始的，所以要置为1，
    for(int i=1;i<=m;i++)dp[0][i]=0;        //不然循环查询的次数多了就会造成错误
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
         if(x[i]==y[j])dp[i][j]=dp[i-1][j-1]+1;
         else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
         //Max=max(Max,dp[i][j]);
        }
    return dp[n][m];
}
int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
         cin>>x>>y;
        cout<<lcs(x,y)<<endl;
    }
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define int long long 

signed main(void){
  
  int q; cin >> q;
  while(q--){
    string s,t; cin >> s >> t;
    int n = s.size(); int m = t.size();
    
    vector<vector<int>> dp(n+10,vector<int>(m+10,0));
    vector<vector<int>> M(n+10,vector<int>(m+10,0));
    
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){ 
        
        if(s[i] == t[j] ){ 
          dp[i+1][j+1] = max(dp[i][j]+1,max(dp[i][j+1],dp[i+1][j]));
        }
        else{
          dp[i+1][j+1] = max(dp[i+1][j],dp[i][j+1]);
        }
        
      }
    }
    
    cout << dp[n][m] << endl;
    
  }
  
  return 0;
}

C++: /*
** Longest Common Subsequence
*/

# include <cstdio>
# include <cstring>
# include <algorithm>
using namespace std;

const int MAX = 1000 + 5;

char s1[MAX], s2[MAX];
int c[MAX][MAX];

int lcs() {
    int m = strlen(s1+1);
    int n = strlen(s2+1);
    c[0][0] = 0;
    int maxl = 0;
    for (int i = 1; i <= m; i++) {
        c[i][0] = 0;
    }
    for (int i = 1; i <= n; i++) {
        c[0][i] = 0;
    }

    for (int i = 1; i <= m; i++) {
        for (int j = 1; j <= n; j++) {
            if (s1[i] == s2[j]) {
                c[i][j] = c[i - 1][j - 1] + 1;
            }
            else {
                c[i][j] = max(c[i][j - 1], c[i - 1][j]);
            }
            maxl = max(maxl, c[i][j]);
        }
    }

    return maxl;
}

void solve() {
    int n;
    scanf("%d", &n);
    while (n--) {
        scanf("%s %s", s1+1, s2+1);
        printf("%d\n", lcs());
    }
}

int main() {
    // freopen("infile", "r", stdin);
    // freopen("outfile", "w", stdout);
    solve();
    return 0;
}

C++: #include <bits/stdc++.h>
#define MAX 1000
using namespace std;
int lcs(string,string);

int main(){
  int i,n;
  string st1,st2;

  cin >> n;
  for(i = 0; i < n; i++){
    cin >> st1 >> st2;
    cout << lcs(st1,st2) << endl;
  }
  return 0;
}

int lcs(string st1,string st2){
  int preMax = 0;
  int m,n,i,j;
  int key[MAX+1][MAX+1];

  m = st1.size();
  n = st2.size();
  /**/
  st1 = ' '+st1;
  st2 = ' '+st2;
  for(i = 1; i <= m; i++){
    key[i][0] = 0;
  }
  for(j = 1; j <= n; j++){
    key[0][j] = 0;
  }
  for(i = 1; i <= m; i++){
    for(j = 1; j <= n; j++){
      if(st1[i] == st2[j]){
        key[i][j] = key[i-1][j-1]+1;
      }
      else{
        key[i][j] = max(key[i-1][j],key[i][j-1]);
      }
      preMax = max(preMax,key[i][j]);
    }
  }
  return preMax;
}