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;
typedef long long ll;
typedef pair<int, int> P;

#define vi vector<int>
#define vl vector<long long>
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define REPD(i, n) for (int i = (int)(n-1); i >= 0; i--)
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define FORD(i, a, b) for (int i = (int)(a); i >= (int)(b); i--)
#define INF 1e18
#define MOD 1e9+7

template<class T> bool chmax(T &a, const T & b) {
    if (a<b) {
        a = b;
        return true;
    }
    return false;
}

template<class T> bool chmin(T &a, const T & b) {
    if (a>b) {
        a = b;
        return true;
    }
    return false;
}

const int MAX_N = 1010;
int dp[MAX_N][MAX_N];
string X, Y;
//dp[i+1][j+1]:Xのi文字目とYのj文字目までのLCS
void LCS(int n, int m) {
    dp[0][0] = 0;
    REP(i, n) {
        REP(j, m) {
            if (X[i] == Y[j]) {
                dp[i+1][j+1] = dp[i][j]+1;
            } else {
                dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
            }
        }
    }
}

int main() {
    int q;
    cin >> q;
    REP(j, q) {
        cin >> X >> Y;
        int n = X.length();
        int m = Y.length();
        LCS(n, m);
        cout << dp[n][m] << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <vector>
#include <queue>
#include <stack>
#include <cmath>
#include <map>
#include <iomanip>
#include <set>
#include <ctime>
#include <tuple>
#include <bitset>
#include <assert.h>
#include <deque>
using namespace std;

/*
using PAIR = pair<string, int>;
sort(sp.begin(), sp.end(), [](PAIR l, PAIR r){
        return l.first<r.first || (l.first==r.first && l.second > r.second);
        });
*/

typedef long long ll;

#define fi first
#define se second
#define rep(i, n) for (ll i = 0; i < n; i++)
#define debugA() cerr << "AAAAA" << endl
#define debug_() cerr << "-------------" << endl
#define debug(x) cerr << #x << ": " << x << endl
#define debug_vec(v)                   \
    for (int i = 0; i < v.size(); i++) \
    {                                  \
        cout << v[i] << " ";           \
    }                                  \
    cout << endl;
#define debug_vec2(v)                         \
    for (int i = 0; i < v.size(); i++)        \
    {                                         \
        for (int j = 0; j < v[i].size(); j++) \
        {                                     \
            cout << v[i][j] << " ";           \
        }                                     \
        cout << endl;                         \
    }

using Graph = vector<vector<int>>;
using P = pair<int, int>;

int main()
{
    int q;
    cin >> q;
    while (q--)
    {
        string s, t;
        cin >> s >> t;
        int n = s.size();
        int m = t.size();
        vector<vector<ll>> dp(n + 10, vector<ll>(m + 10, 0));
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= m; j++)
            {
                if (s[i - 1] == t[j - 1])
                {
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 1);
                }
                else
                {
                    dp[i][j] = max({dp[i][j], dp[i - 1][j], dp[i][j - 1]});
                }
            }
        }
        // debug_vec2(dp);
        cout << dp[n][m] << endl;
    }

    return 0;
}

C++: #include<bits/stdc++.h>
#define rep(i, n) for(int (i) = 0; (i) < (n); (i)++)
#define print(x) cout << (x) << endl;
#define printa(x, n) for(ll i = 0; i < n; i++) {cout << (x[i]) << " ";}
using namespace std;
using ll = long long;

int dp[1005][1005];
vector<int> ans;

int main(void) {
    int q;
    cin >> q;
    rep (_, q) {
        string s, t;
        cin >> s >> t;

        rep (i, 1002) rep (j, 1002) dp[i][j] = 0;


        for (int si = 1; si <= s.size(); si++) {
            for (int ti = 1; ti <= t.size(); ti++) {
                if (s[si - 1] == t[ti - 1]) {
                    dp[si][ti] = dp[si - 1][ti - 1] + 1;
                }
                else {
                    dp[si][ti] = max(dp[si - 1][ti], dp[si][ti - 1]);
                }
            }
        }
        ans.push_back(dp[s.size()][t.size()]);
    }
    
    rep (i, q) cout << ans[i] << endl;
    return 0;
}

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

void CSLength(char *,char *);

int c[1000][1000],a[1000];

int main() {
  int i,j=0,q;
  char s[1000],x[1000],y[1000];

  scanf("%d",&q);

  for(i=0;i<q;i++){

    scanf("%s",s);
    strcpy(&x[1],s);

    scanf("%s",s);
    strcpy(&y[1],s);

    CSLength(x,y);
    a[i]=c[strlen(x)-1][strlen(y)-1];
  }

  for(i=0;i<q;i++){
    printf("%d\n",a[i]);
  }

  return 0;
}

void CSLength(char *x,char *y){
  int m,n,i,j;

  m = strlen(x);
  n = strlen(y);

  for(i=1;i<m;i++) c[i][0] = 0;
  for(j=1;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 if(c[i-1][j] >= c[i][j-1]){
	c[i][j] = c[i-1][j];
      }
      else c[i][j] = c[i][j-1];
    }
  }
}

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();

  for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
      if (X[i] == Y[j]) 
        if (i == 0 || j == 0) 
          c[i][j] = 1;
        else 
          c[i][j] = c[i - 1][j - 1] + 1;
      else
        c[i][j] = max(c[i][j - 1], c[i - 1][j]);
    }
  }
  return c[m - 1][n - 1];
}

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;
}