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(){
	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 <iostream>
#include <stdio.h>
#include <string>
#include <algorithm>

using namespace std;

#define N 1000

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

	X = ' ' + X;
	Y = ' ' + 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] == 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(void){

	string s1,s2;
	int i,n;

	scanf("%d",&n);
	for(i=0;i<n;i++){
		cin >> s1 >> s2;
		cout << lcs(s1,s2) << endl;
		//printf("%d\n",lcs(s1,s2));
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <cstdio>
#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 = 1; 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;
int ans = lcs(s1, s2);
printf("%d\n", ans);
}
return 0;
}

C++: v#include <iostream>
#include <string>
#include <algorithm>

//#define FOR(i,a,b) for(int i=(a);i<(b);++i)
//#define REP(i,n)  FOR(i,0,n)

using namespace std;

static const int N = 10000;

// longest common sequence
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 = 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 <cstring>
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,a) repi(i,0,a)
#define clr(a,v) memset((a),(v),sizeof(a))

int q;
int dp[1000][1000];
std::string s, t;

int rec( int i, int j )
{
  int &ret = dp[i][j];

  if( ~ret )
    return ret;

  if( i == s.size() || j == t.size() )
    return 0;

  ret = 0;

  if( s[i] == t[j] )
    ret = std::max( ret, rec( i+1, j+1 )+1 );

  ret = std::max( ret, std::max( rec( i+1, j ), rec( i, j+1 ) ) );

  return ret;
}

int main()
{
  scanf( "%d", &q );
  while( q-- )
  {
    std::cin >> s >> t;

    clr( dp, -1 );

    std::cout << rec( 0, 0 ) << std::endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> Vi;
typedef tuple<int, int, int> T;
#define FOR(i,s,x) for(int i=s;i<(int)(x);i++)
#define REP(i,x) FOR(i,0,x)
#define ALL(c) c.begin(), c.end()
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

int dp[2][1024];

int main() {
  // use scanf in CodeForces!
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N;
  cin >> N;
  REP(q, N) {
    string X, Y;
    cin >> X >> Y;
    int LX = X.size(), LY = Y.size();
    REP(i, 2) REP(j, LY+1) dp[i][j] = 0;
    REP(i, LX) REP(j, LY) {
      if (X[i] == Y[j]) {
	dp[(i+1)%2][j+1] = dp[i%2][j] + 1;
      } else {
	dp[(i+1)%2][j+1] = max(dp[(i+1)%2][j], dp[i%2][j+1]);
      }
    }
    cout << dp[LX%2][LY] << endl;
  }
  return 0;
}

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

int main() {
  int q; cin >> q;
  string A, B;
  for (int i=0; i<q; i++) {
    cin >> A >> B;
    vector<vector<int>> LCS(A.length()+1, vector<int>(B.length()+1,0));
    int ans=0;
    for (int j=1; j<=A.length(); j++) {
      for (int k=1; k<=B.length(); k++) {
        if(A[j]==B[k]) LCS[j][k]=LCS[j-1][k-1]+1;
        else LCS[j][k]=max(LCS[j-1][k],LCS[j][k-1]);
        ans = max(ans, LCS[j][k];
      }
    }
    cout << ans << "\n";
  }
}

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; //X[0]?????????????????\
    Y = ' ' + Y; //Y[0]?????????????????\
    for ( int i = 1; 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 <vector>
#include <algorithm>

using namespace std;

const int MAXN = 1010;

int main(int argc, char const *argv[]) {
  int q;
  cin >> q;
  for (auto k = 0; k < q; k++) {
    vector<vector<int>> dp(MAXN, vector<int>(MAXN, 0));
    string s1, s2;
    cin >> s1 >> s2;
    auto n = s1.size();
    auto m = s2.size();
    for (size_t i = 0; i < n; i++) {
      for (size_t j = 0; j < m; j++) {
        if (s1[i] == s2[j]) {
          dp[i + 1][j + 1] = dp[i][j] + 1;
        } else {
          dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
        }
      }
    }
    cout << dp[n][m] << endl;
  }

  return 0;
}