Go: package main

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

func max(x, y int) int {
	if x < y {
		return y
	} else {
		return x
	}
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	n, _ := strconv.Atoi(scanner.Text())
	for i := 0; i < n; i++ {
		scanner.Scan()
		s1 := scanner.Text()
		scanner.Scan()
		s2 := scanner.Text()
		s1, s2 = " " + s1 , " " + s2
		c := make([][]int, len(s1))
		for i := range c {
			c[i] = make([]int, len(s2))
		}

		LCS := 0

		for i := 1; i < len(s1); i++ {
			for j := 1; j < len(s2); j++ {
				if s1[i] == s2[j] {
					c[i][j] = c[i-1][j-1] + 1
				} else {
					c[i][j] = max(c[i-1][j], c[i][j-1])
				}
				LCS = max(LCS, c[i][j])
			}
		}
		fmt.Println(LCS)
	}
}

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define forever while (true)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
template<typename A> using V = std::vector<A>;
template<typename A> using F = std::function<A>;
template<typename A, typename B> using P = std::pair<A, B>;
using pii = P<int, int>;
using vi = V<int>;
using vd = V<double>;
using vs = V<std::string>;
using vpii = V<pii>;
using vvi = V<vi>;
using vvpii = V<vpii>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
template<typename T> std::istream &operator>>(std::istream &is, std::vector<T> &v) { for (T &x : v) is >> x; return is; }
using namespace std;
// clang-format on

main {
  int n;
  cin >> n;
  while (n--) {
    string x, y;
    cin >> x >> y;
    vvi dp(x.size() + 1, vi(y.size() + 1));
    dp[0][0] = 0;
    loop(i, 1, x.size() + 1) loop(j, 1, y.size() + 1) {
      if (x[i - 1] == y[j - 1]) {
        dp[i][j] = dp[i - 1][j - 1] + 1;
        continue;
      }
      dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
    }
    cout << dp.back().back() << endl;
  }
}

C++: #define _CRT_SECURE_NO_WARNINGS
#pragma warning(disable: 4244) // 最悪をします
#include <iostream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <numeric>
#include <queue>
#include <stack>
#include <map> 
#include <set>
#include <string>
#include <functional>
#include <list>
#include <random>
#include <time.h>
#include <iomanip>
#include <assert.h>
#include <numeric>
#include <sstream>
#define BIT(nr) (1UL << (nr))
#define int long long
//#define ll long long
#define double long double
#define mod 1000000007
#define MAXN (int)1e+5 * 2+1
#define LL_MAX 9223372036854775807	//ない環境用
#define LL_HALFMAX 9223372036854775807 / 2	//ない環境用
#define MIN -(9223372036854775807 / 2)
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
#define REPS(i,x) for(int i=1;i<=(int)(x);i++)
#define RREP(i,x) for(int i=((int)(x)-1);i>=0;i--)
#define RREPS(i,x) for(int i=((int)(x));i>0;i--)
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define mp make_pair
template<typename T1, typename T2> inline void chmin(T1 & a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }


using namespace std;

//デバッグ用カッコの有無
#ifdef DEBUG
template <class T>ostream &operator<<(ostream &o, const vector<T>&v)
{
	o << "{"; for (int i = 0; i<(int)v.size(); i++)o << (i>0 ? ", " : "") << v[i]; o << "}"; return o;
}
#endif // DEBUG

template <class T>ostream &operator<<(ostream &o, const vector<T>&v)
{
	for (int i = 0; i<(int)v.size(); i++)o << (i>0 ? " " : "") << v[i]; return o;
}

int dx[4] = { 0, 1, 0, -1 }; // x軸方向への変位
int dy[4] = { 1, 0, -1, 0 }; // y軸方向への変位

int dxp[4] = { 0, 1 }; // x軸方向への変位(正のみ)
int dyp[4] = { 1, 0 }; // y軸方向への変位(負のみ)

using Weight = int;
using Flow = int;
struct Edge {
	int src, dst;

	// libalgo のものに追加、メンバを追加するだけなので互換性は崩さないはず、逆辺のG[e.dstの]インデックスを保持
	int rev;
	Weight weight;
	Flow cap;
	Edge() : src(0), dst(0), weight(0) {}
	Edge(int s, int d, Weight w) : src(s), dst(d), weight(w) {}
};
using Edges = std::vector<Edge>;
using Graph = std::vector<Edges>;
using Array = std::vector<Weight>;
using Matrix = std::vector<Array>;

void add_edge(Graph& g, int a, int b, Weight w = 1) {
	g[a].emplace_back(a, b, w);
	g[b].emplace_back(b, a, w);
}
void add_arc(Graph& g, int a, int b, Weight w = 1) { g[a].emplace_back(a, b, w); }

void solve() {

}

int dp[30][50010];

signed main() {
	int q;
	cin >> q;

	rep(_, q) {
		string s, t;
		cin >> s >> t;
		int sl = s.length();
		int tl = t.length();

		s = "*" + s;
		t = "*" + t;

		vector<vector<int>> dp(sl + 1, vector<int>(tl + 1, 0));

		REPS(i, sl) {
			REPS(j, tl) {
				if (s[i] == t[j]) {
					chmax(dp[i][j], dp[i - 1][j - 1] + 1);
				}
				chmax(dp[i][j], dp[i - 1][j]);
				chmax(dp[i][j], dp[i][j - 1]);

			}
		}

		cout << dp[sl][tl] << "\n";
	}

}

C++: #include<cstdlib>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
#include<queue>
#include<set>
using namespace std;
const int MAXN = (int)1e3 + 10;
const int INF = (int) 0x3f3f3f3f;
typedef long long LL;

int n;
int dp[MAXN][MAXN];
char a[MAXN],b[MAXN];

void work(){
    int q; scanf("%d",&q);
    while(q--){
        scanf("%s%s",a+1,b+1);
        int lena=strlen(a+1);
        int lenb=strlen(b+1);
        for(int i=1;i<=lena;i++)
            for(int j=1;j<=lenb;j++) dp[i][j]=INF;
        for(int i=1;i<=lena;i++){
            for(int j=1;j<=lenb;j++){
                dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
                dp[i][j]=max(dp[i][j],dp[i-1][j-1]+(a[i]==b[j]));
            }
        }
        printf("%d\n",dp[lena][lenb]);
    }
}
/*
3
abcbdab
bdcaba
abc
abc
abc
bc
*/

int main(){
    work();
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
#define inf (int)(1e9+7)
#define abs(x) (x >= 0 ? x : -(x))
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }
template<typename T> inline T gcd(T a, T b) { if (b == 0) return a; return gcd(b, a % b); }







int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    
    
    
    int n;
    cin >> n;
    while (n--) {
        string s, t;
        cin >> s >> t;
        int dp[1003][1003] = {0};
        rep(i, sz(s) + 1) rep(j, sz(t) + 1) {
            chmax(dp[i + 1][j], dp[i][j]);
            chmax(dp[i][j + 1], dp[i][j]);
            chmax(dp[i + 1][j + 1], dp[i][j] + (s[i] == t[j]));
        }
        cout << dp[sz(s)][sz(t)] << endl;
        // rep(i, sz(s) + 1) { rep(j, sz(t) + 1) cout << dp[i][j] << " "; cout << endl; }
    }
}