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] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// 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 <bits/stdc++.h>
using namespace std;
using ll=long long;
using vb=vector<bool>;
using vvb=vector<vb>;
using vd=vector<double>;
using vvd=vector<vd>;
using vi=vector<int>;
using vvi=vector<vi>;
using vl=vector<ll>;
using vvl=vector<vl>;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll>;
using vs=vector<string>;
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define rep(i,n) range(i,0,n)
#define range(i,a,n) for(ll i=(a);i<(n);i++)
#define LINF ((ll)1ll<<60)
#define INF ((int)1<<30)
#define EPS (1e-9)
#define MOD (1000000007ll)
#define fcout(a) cout<<setprecision(a)<<fixed
#define fs first
#define sc second
#define PI 3.1415926535897932384

int dx[]={1,0,-1,0,1,-1,-1,1},dy[]={0,1,0,-1,1,1,-1,-1};
template<class S,class T>ostream&operator<<(ostream&os,pair<S,T>p){os<<"["<<p.first<<", "<<p.second<<"]";return os;};
template<class S>auto&operator<<(ostream&os,vector<S>t){bool a=1; for(auto s:t){os<<(a?"":" ")<<s;a=0;} return os;}
void OUT(bool b){cout<<(b?"YES":"NO")<<endl;}
void Out(bool b){cout<<(b?"Yes":"No")<<endl;}
void out(bool b){cout<<(b?"yes":"no")<<endl;}
template<class T>
void puta(T&&t){cout<<t<<endl;}
template<class H,class...T>
void puta(H&&h,T&&...t){cout<<h<<' ';puta(t...);}

int popcnt(int x){return __builtin_popcount(x);}
int popcnt(ll x){return __builtin_popcountll(x);}
int bsr(int x){return 31 - __builtin_clz(x);}
int bsr(ll x){return 63 - __builtin_clzll(x);}
int bsf(int x){return __builtin_ctz(x);}
int bsf(ll x){return __builtin_ctzll(x);}
template<class T>T chmax(T&a,T b){return a=a>b?a:b;}
template<class T>T chmin(T&a,T b){return a=a<b?a:b;}
/*他のライブラリを入れる場所*/

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int d;
	cin>>d;
	rep(_,d){
		string s,t;
		cin>>s>>t;
		int n=s.size(),m=t.size();
		vvi dp(n+1,vi(m+1,0));
		rep(i,n){
			dp[i+1]=dp[i];
			rep(j,m){
				if(s[i]==t[j]){
					chmax(dp[i+1][j+1],dp[i][j]+1);
				}else{
					chmax(dp[i+1][j+1],dp[i+1][j]);
				}
			}
	//		cout<<dp[i]<<endl;
		}
	//	cout<<dp[n]<<endl;
		cout<<dp[n][m]<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <stdio.h>
#include <string>
#include <cmath>

#define MAX_LENGTH 1000
#define NIL -1
using namespace std;
//think easy make easy

int q;//num of datasets
string X;
string Y;
char map[MAX_LENGTH+1][MAX_LENGTH+1];

int findMaxLength(int x,int y){//x:Xの終端.y:Yの終端(0オリジン)
	int val;

	if(x == 0 || y == 0) return 0;

	if(map[x][y] == NIL){
		if(X.at(x) == Y.at(y)){
			val = findMaxLength(x-1,y-1) +1;
		}else{
			val = max(findMaxLength(x-1,y),findMaxLength(x,y-1));
		}
		map[x][y] = val;//メモ
		return val;
	}else return map[x][y];
}

int main(){
	
	scanf("%d",&q);

	for(int i=0;i<q;i++){
		cin >>X; cin >> Y;
		for(int i=0;i<X.size();i++){
			for(int j=0;j<Y.size();j++){
				map[i][j] = NIL;
			}
		}
	
		cout <<findMaxLength(X.size()-1,Y.size()-1) <<endl;
	}

	return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
static const int N =1000;

int lcs(string X,string Y){
  int c[N+1][N+1];
  int m=X.size();
  int n=Y.size();
  int maxl=0;
  X=' '+X;
  Y=' '+Y;
  for(int i=0;i<=m;i++)c[i][0]=0;
  for(int j=1;j<=n;j++)c[0][j]=0;

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

int main(){
  string s1,s2;
  int n;cin>>n;
  for(int i=0;i<n;i++){
    cin>>s1>>s2;
    cout<<lcs(s1,s2)<<endl;
  }
return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
static const int N = 1000;

int lcs(string X, string Y) {
  int c[N + 1][N + 1];
  int m = X.size();
  int n = Y.size();
  int maxl = 0;
  X = ' ' + X;
  Y = ' ' + Y;
  for ( int i = 0; i <= m; i++ ) c[i][0] = 0;
  for ( int j = 1; j <= n; j++ ) c[0][j] = 0;

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

  return maxl;
}

int main() {
  string s1, s2;
  int n; cin >> n;
  for ( int i = 0; i < n; i++ ) {
    cin >> s1 >> s2;
    cout << lcs(s1, s2) << endl;
  }
  return 0;
}

C++: #include <stdio.h>
#include <string.h>
#define N 1000

void Ics(char *X, char *Y)
{
   int c[N][N];
   int m, n, i, j;

   m = strlen(X);
   n = strlen(Y);

   for ( i = 1; i <= m; i++ ) c[i][0] = 0;
   for ( j = 0; j <= n; j++ ) c[0][j] =0;
   for ( i = 1; i <= m; i++ ) {
      for ( j = 1; j <=n; j++ ) {
         if ( X[ i - 1 ] == Y[ j - 1] ) c[ i ][ j ] = c[ i - 1 ][ j - 1 ] + 1;
         else if ( c[ i - 1 ][ j ] >= c[ i ][ j - 1 ] )c[ i ][ j ] = c[ i - 1 ][ j ];
         else c[ i ][ j ] = c[ i ][ j - 1 ];
      }
   }
   printf("%d\n", c[ m ][ n ]);
}
     
int main()
{
   int n, i;
   char X[N], Y[N];

   scanf("%d", &n);
   for ( i = 0; i < n; i++ ) {
      scanf("%s%s", X, Y);
      Ics(X, Y);
   }
   return 0;
}