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 <iostream>

//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <tuple>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s)
{
    int v;
    istringstream sin(s);
    sin >> v;
    return v;
}
template <class T>
inline string toString(T x)
{
    ostringstream sout;
    sout << x;
    return sout.str();
}

//math
//-------------------------------------------
template <class T>
inline T sqr(T x) { return x * x; }

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())

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

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);

//clear memory
#define CLR(a) memset((a), 0, sizeof(a))

//debug
// #define dump(x) cerr << #x << " = " << (x) << endl;
// #define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" \
//                       << " " << __FILE__ << endl;

class LCS_Solver
{
    vector<VL> vl;
    string &s1;
    string &s2;

public:
    LCS_Solver(size_t s, string &s1, string &s2)
        : vl(s, VL(s, -1)), s1(s1), s2(s2)
    {
        vl[0][0] = 0;
        REP(i, s)
        {
            vl[0][i] = 0;
            vl[i][0] = 0;
        }
    }

    LL solve_memoize(int s1n, int s2m);
    LL solve_dp(int s1n, int s2m) const;
};

LL LCS_Solver::solve_memoize(int s1n, int s2m)
{
    // cout << s1n << ", " << s2m << endl;
    if (vl[s1n][s2m] >= 0)
    {
        return vl[s1n][s2m];
    }
    else
    {
        LL ans;
        if (s1[s1n - 1] == s2[s2m - 1])
        {
            ans =
                solve_memoize(s1n - 1, s2m - 1) + 1;
            vl[s1n][s2m] = ans;
            return ans;
        }
        else
        {
            ans = max(
                solve_memoize(s1n - 1, s2m),
                solve_memoize(s1n, s2m - 1));
            vl[s1n][s2m] = ans;
            return ans;
        }
    }
}

const size_t MAX_SIZE = 2000;

int main()
{
    int n;
    cin >> n;

    LL ans;
    REP(_, n)
    {
        string s1, s2;
        cin >> s1;
        cin >> s2;
        // cout << s1.size() << " " << s2.size() << endl;

        ans = LCS_Solver(MAX_SIZE, s1, s2)
                  .solve_memoize(s1.size(), s2.size());
        cout << ans << endl;
    }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define  all(x) (x).begin(),(x).end()
typedef long long ll;

int c[1005][1005];

int lcs(string s1, string s2){
    int n = s1.size();
    int m = s2.size();
    s1 = " " + s1;
    s2 = " " + s2;
    for(int i = 0; i <= n; i++) c[i][0] = 0;
    for(int i = 0; i <= n; i++) c[0][i] = 0;

    int ans = 0;
    for (int i1 = 1; i1 <= n; i1++){
        for(int i2 = 1; i2 <= m; i2++){
            if(s1[i1] == s2[i2]){
                c[i1][i2] = c[i1-1][i2-1] + 1;
            }else{
                c[i1][i2] = max(c[i1-1][i2], c[i1][i2-1]);
            }
        }
        ans = max(ans, c[i1][m]);
    }
    return ans;
}

int main(){
    int q;
    cin >> q;
    vector<int> ans(q);
    for(int i = 0; i < q; i++){
        string s1, s2;
        cin >> s1 >> s2;
        ans[i] = lcs(s1, s2);
    }
    rep(i,q) cout << ans[i] << endl;
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const ld EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

int main(){
    int T;
    cin >> T;
    while(T--){
        string a, b;
        cin >> a >> b;
        int M = sz(a), N = sz(b);
        int dp[M+1][N+1];
        rep(i, M+1) dp[i][0] = 0;
        rep(j, N+1) dp[0][j] = 0;
        rep(i, M){
            rep(j, N){
                if(a[i] == b[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[M][N] << endl;
    }
}