Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

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

// Longest Common Subsequence

class LCS {
    string S, T;
    vector <vector<int>> dp;

public:
    LCS(string &s, string &t) : S(s), T(t) {
        int sl = S.size(), tl = T.size();
        dp.assign(sl + 1, vector<int>(tl + 1, 0));

        for (int i = 0; i < sl; i++) {
            for (int j = 0; j < tl; j++) {
                if (S[i] == T[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 len() { return dp[S.size()][T.size()]; }

    string str() {
        string ret = "";
        int i = S.size(), j = T.size();
        while (dp[i][j]) {
            if (S[i - 1] == T[j - 1]) {
                i--, j--;
                ret = S[i] + ret;
            } else if (dp[i - 1][j] > dp[i][j - 1]) {
                i--;
            } else {
                j--;
            }
        }
        return ret;
    }
};


// verified
//   http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_10_C&lang=jp
void AOJ_ALDS1_10_C() {
    int q;
    cin >> q;
    while (q--) {
        string x, y;
        cin >> x >> y;
        LCS lcs(x, y);
        cout << lcs.len() << "\n";
    }
}


// verified
//   https://atcoder.jp/contests/dp/tasks/dp_f
void AtCoder_2019_1_6_F() {
    string s, t;
    cin >> s >> t;
    LCS lcs(s, t);
    cout << lcs.str() << '\n';
}

int main() {
    AOJ_ALDS1_10_C();
    // AtCoder_2019_1_6_F();
    return 0;
}

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

using namespace std;
typedef long long ll;
typedef long int li;
typedef long double lb;
#define rep(i,j,n) for (ll i = j; i < (n); i++)
#define repr(i,j,n) for(ll i = j; i >= (n); i--)
#define all(x) (x).begin(),(x).end()
#define CLR(mat,f) memset(mat, f, sizeof(mat))
#define IN(a, b, x) (a<=x&&x<b)
#define out(ans) cout << ans << endl
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
typedef pair<ll,ll>P;
const ll mod=1e9+7;
const ll INF = 1LL<<60;
const ll m=1LL<<32;

const ll MAX_N=1001;

ll lcs(string a,string b){

  ll c[MAX_N][MAX_N];
  ll as=a.size();
  ll bs=b.size();
  a.insert(0," ");
  b.insert(0," ");

  CLR(c,0);
  rep(i,1,as+1){
    rep(j,1,bs+1){
      if(a[i]==b[j])c[i][j]=c[i-1][j-1]+1;
      else chmax(c[i][j],max(c[i-1][j],c[i][j-1]));
    }
  }

  return c[as][bs];
}

int main(){

  ll n;cin>>n;

  while(n--){
    string a,b;cin>>a>>b;
    out(lcs(a,b));
  }

  return 0;
}

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

int Longest(string x, string y) {
  int L[1001][1001];
  int maxl = -1;
  int xlen = x.size();
  int ylen = y.size();

  x = ' ' + x;
  y = ' ' + y;

  for (int i = 1; i <= xlen; i++) L[i][0] = 0;
  for (int j = 1; j <= ylen; j++) L[0][j] = 0;

  for (int i = 1; i <= xlen; i++) {
    for (int j = 1; j <= ylen; j++) {
      if (x[i] == y[j])
        L[i][j] = L[i-1][j-1] + 1;
      else
        L[i][j] = max(L[i][j-1], L[i-1][j]);

      maxl = max(maxl, L[i][j]);
    }
  }

  return maxl;
}

int main() {
  string X, Y;
  int n;
  int result[10000];

  cin >> n;

  for (int i = 0; i < n; i++) {
    cin >> X;
    cin >> Y;
    result[i] =  Longest(X, Y);
    cout << result[i] << endl;
  }

  return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long ll;
typedef long long ll;
ll q, dp[1010][1010];
string s, t;
int main(void){
    // Your code here!
    cin >> q;
    for (ll k = 0; k < q; k++) {
        cin >> s >> t;
        for (ll i = 1; i <= s.length(); i++) {
            for (ll j = 1; j <= t.length(); j++) {
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
                if (s[i - 1] == t[j - 1]) {
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 1);
                }
            }
        }
        cout << dp[s.length()][t.length()] << endl;
    }
}

C++: #include <iostream>
#include <vector>
#include <map>
#include <algorithm>
#include <queue>
#include <string>
#define REP(i,a,b) for (int i = a; i < (b); i++)
#define sz(t) int(t.size())
#define INF 1000000000
const int DIV = 1000000000 + 7;
using namespace std;
typedef long long ll;

int solve(string x, string y) {
    int dp[1050][10050];
    x = ' ' + x;
    y = ' ' + y;
    int lx = x.size();
    int ly = y.size();
    REP(i, 0, lx) dp[0][i] = 0;
    REP(i, 0, ly) dp[i][0] = 0;
    int ans = 0;
    REP(i, 1, ly) {
        REP(j ,1, lx) {
            if (y[i] == x[j]) {
                dp[i][j] = dp[i - 1][j - 1] + 1;
            } else {
                dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
            }  
            ans = max(ans, dp[i][j]);
        }
    }

    return ans;
}

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

    REP(i, 0, n) {
        string x, y;
        cin >> x;
        cin >> y;
        cout << solve(x, y) << endl;
    }
}

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

int Longest(string x, string y) {
  int L[1001][1001];
  int maxl = -1;
  int xlen = x.size();
  int ylen = y.size();

  x = ' ' + x;
  y = ' ' + y;

  for (int i = 1; i <= xlen; i++) L[i][0] = 0;
  for (int j = 1; j <= ylen; j++) L[0][j] = 0;

  for (int i = 1; i <= xlen; i++) {
    for (int j = 1; j <= ylen; j++) {
      if (x[i] == y[j]) {
        L[i][j] = L[i-1][j-1] + 1;
      } else {
        L[i][j] = max(L[i][j-1], L[i-1][j]);
        }
      maxl = max(maxl, L[i][j]);
    }
  }

  return maxl;
}

int main() {
  string X, Y;
  int n;
  cin >> n;

  for (int i = 0; i < n; i++) {
    cin >> X;
    cin >> Y;
    cout << Longest(X, Y) << endl;
  }

  


  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n,x) for(int i=n;i<x;i++)
const int MAX_N = 1000;

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

    int dp[MAX_N+1][MAX_N+1];

    while(q > 0){
        string x, y; cin >> x >> y;

        int X = x.size(), Y = y.size();
        rep(i, 0, X){
            rep(j, 0, Y){
                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]);
            }
        }

        cout << dp[X][Y] << endl;

        q--;
    }

    return 0;
}