Go: package main

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

const (
	initialBufSize = 100000
	maxBufSize     = 1000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	resolve()
}

func resolve() {
	n := scanInt(sc)
	results := []int{}
	for i := 0; i < n; i++ {
		results = append(results, resolveInstance())
	}
	for _, v := range results {
		fmt.Println(v)
	}
	return
}

func resolveInstance() int {
	x, y := scanString(sc), scanString(sc)
	lx, ly := len(x), len(y)
	dp := make([][]int, lx+1)
	dp[0] = make([]int, ly+1)
	for i := 1; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
		dp[i][0] = dp[i-1][0]
		for j := 1; j <= ly; j++ {
			dp[i][j] = dp[i-1][j]
			if dp[i][j] < dp[i][j-1] {
				dp[i][j] = dp[i][j-1]
			}
			if x[i-1] == y[j-1] {
				cL := dp[i-1][j-1] + 1
				if dp[i][j] < cL {
					dp[i][j] = cL
				}
			}
		}
	}
	return dp[lx][ly]
}

const (
	remove = 0 + iota
	match
)

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

#define FOR( i, m, n )  for( int (i) = (m); (i) < (n); (i)++ )
#define REP( i, n )     FOR( i, 0, n )
#define ALL( a )        (a).begin(), (a).end()             

int	dp[1001][1001] = {};

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

	int maxl;

	string s1, s2;
	REP( i, n ) {
		cin >> s1 >> s2;
		maxl = 0;
		memset( dp, 0, sizeof( int ) );
		FOR( j, 1, s1.size() + 1 ) {
			FOR( k, 1, s2.size() + 1 ) {
				if( s1[j] == s2[k] ) {
					dp[j][k] = dp[j - 1][k - 1] + 1;
				} else {
					dp[j][k] = max( dp[j - 1][k], dp[j][k - 1] );
				}
				maxl = max( dp[j][k], maxl );
			}
		}

		cout << maxl << endl;
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

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

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

// ---------------------
#define INF 922337203685477580
typedef long long ll;

int dp[1000][1000];

int main() {
  int q;
  cin >> q;
  REP(loop, q) {
    char S[1000], T[1000];
    cin >> S >> T;

    dp[0][0] = 0;
    for (int i = 0; i < strlen(S); i++) {
      for (int j = 0; j < strlen(T); j++) {
        if (S[i] == T[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[strlen(S) - 1][strlen(T) - 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; //insert a space to X[0]
    Y = ' ' + Y; //insert a space to Y[0]
    
    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"cstring"
using namespace std;

int c[1001][1001];
void lcs(char*a,char*b)
{
	int m = strlen(a);
	int n = strlen(b);
	int i, j;
	for(i=0;i<1001;++i)
	{
		c[0][i] = 0;
		c[i][0] = 0;
	}
	for (i = 1; i <= m; ++i)
		for (j = 1; j <= n; ++j)
			if (a[i-1] == b[j-1])c[i][j] = c[i - 1][j - 1] + 1;
			else c[i][j] = c[i][j - 1] > c[i - 1][j] ? c[i][j - 1] : c[i - 1][j];
	cout<<c[m][n]<<endl;
}
int main()
{
	int n,i;
	cin >> n;
	cin.get();
	char** a = new char* [2 * n];
	for (i = 0; i < 2 * n; ++i)
	{
		a[i] = new char[1001];
		cin.getline(a[i], 1001);
	}
	for (i = 0; i < 2 * n; i += 2)
		lcs(a[i], a[i + 1]);
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxx = 1010;
int c[maxx][maxx];

int lcs(char s1[],char s2[]) {
    int m = strlen(s1), n = strlen(s2);
    for (int i = 1; i <= m; i++)
        c[i][0] = 0;
    for (int i = 1; i <= n; i++)
        c[0][i] = 0;

    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            if (s1[i] == s2[j])
                c[i+1][j+1] = c[i][j] + 1;
            else
                c[i+1][j+1] = max(c[i][j+1], c[i + 1][j]);
        }
    }
    return c[m][n];
}
int main()
{
    char s1[maxx], s2[maxx];
    int t;
    scanf("%d", &t);
    for (int i = 0; i < t; i++) {
        scanf("%s %s", s1, s2);
        printf("%d\n",lcs(s1,s2));
    }

    return 0;
}

C++: #include <iostream>
#include <string>
using namespace std;

int main(void){
    int q; cin >> q;
    int dp[1001][1001];
    for(int i = 0; i < 1001; i++) dp[0][i] = dp[i][0] = 0;

    for(int i = 0; i < q; i++){
        string a, b; cin >> a >> b;
        int len_a = (int)a.size(), len_b = (int)b.size();
        for(int j = 1; j <= len_a; j++){
            for(int k = 1; k <= len_b; k++){
                if(a[j]==b[k]) dp[j][k] = dp[j-1][k-1] + 1;
                else dp[j][k] = max(dp[j-1][k], dp[j][k-1]);
            }
        }

        cout << dp[len_a][len_b] << '\n';
    }

    return 0;
}

C++: #include "bits/stdc++.h"
#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define FOR(i, a) for (auto &i: a)
#define ALL(obj) begin(obj), end(obj)
#define MAX(x) *max_element(ALL(x))
#define MIN(x) *min_element(ALL(x))
#define sum(x) accumulate(ALL(x), 0LL)
#define LOWER_BOUND(A, key) distance(A.begin(), lower_bound(ALL(A), key))
#define UPPER_BOUND(A, key) distance(A.begin(), upper_bound(ALL(A), key))

using namespace std;
const int MOD    = (int)(1e9 + 7);
const int INF    = (int)(1e13 + 7);
const double EPS = 1e-14;
const double PI  = acos(-1);

int CEIL(int a, int b) { return (a >= 0 ? (a + (b - 1)) / b : (a - (b - 1)) / b); } //ceil() for int
int mod(int a, int b) { return a >= 0 ? a % b : a - (b * CEIL(a, b)); }             //always return positive num
int bpm(int a, int b) {                                                             //return x^y in order(log(y))
  int res = 1;
  for (a %= MOD; b; a = a * a % MOD, b >>= 1)
    if (b & 1) res = res * a % MOD;
  return res;
}

struct LCS {
private:
  vector<vector<int>> dp;
  string one, two;
  int n1, n2;

public:
  LCS(string &temp1, string &temp2): n1(temp1.size()), n2(temp2.size()) {
    one = temp1;
    two = temp2;
    dp.assign(n1 + 1, vector<int>(n2 + 1, 0));
  }
  int lcs() {
    for (int i = 0; i < n1; i++) {
      for (int j = 0; j < n2; j++) {
        if (one[i] == two[j]) {
          dp[i + 1][j + 1] = max({dp[i][j] + 1, dp[i + 1][j], dp[i][j + 1]});
        } else {
          dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j]);
        }
      }
    }
    return dp[n1][n2];
  }
};

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  rep(_, n) {
    string temp1, temp2;
    cin >> temp1 >> temp2;
    LCS lcs(temp1, temp2);
    cout << lcs.lcs() << endl;
  }
}