Go: package main

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

var sc = bufio.NewScanner(os.Stdin)

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func lcs(a, b string) int {
	lenA := len(a)
	lenB := len(b)
	dp := make([][]int, lenA+1)
	for i := range dp {
		dp[i] = make([]int, lenB+1)
	}

	for i := 1; i <= lenA; i++ {
		for j := 1; j <= lenB; j++ {
			if a[i-1] == b[j-1] {
				dp[i][j] = dp[i-1][j-1] + 1
			} else {
				dp[i][j] = max(dp[i][j-1], dp[i-1][j])
			}
		}
	}
	return dp[lenA][lenB]
}

func main() {
	n := scanInt()
	w := bufio.NewWriter(os.Stdout)
	for i := 0; i < n; i++ {
		a := scanString()
		b := scanString()
		fmt.Fprintln(w, lcs(a, b))
	}
	w.Flush()
}

C++: //#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin(), v.end()
using in = int64_t;
#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++)
const double PI=3.14159265358979323846;
const in MOD = 1000000007;
const in INF=1<<30;
using P=pair<int,int>;
vector<int> dx={0,1,-1,0};
vector<int> dy={1,0,0,-1};

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

int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cout << fixed << setprecision(10);
    int n;
    cin>>n;
    rep(count_num,n){
        string x,y;
        cin>>x>>y;
        int s=x.size(),t=y.size();
        vector<vector<int>> dp(s+1,vector<int>(t+1,-1));
        dp[0][0]=0;
        rep(i,s+1)rep(j,t+1){
            if(i+j==0) continue;
            if(i>0) chmax(dp[i][j],dp[i-1][j]);
            if(j>0) chmax(dp[i][j],dp[i][j-1]);
            if(i*j>0 && x[i-1]==y[j-1]) chmax(dp[i][j],dp[i-1][j-1]+1);
        }
        cout<<dp[s][t]<<'\n';
    }
}

C++: #include<iostream>
#include<cstdio>

using namespace std;

int maxa[1000];
int main(){
  int n;
  int k;
  int count;
  cin>>n;
  char X[1001];
  char Y[1001];
  for(int i=0;i<n;i++){
    cin>>X;
    cin>>Y;

    for(int a=0;Y[a]!='\0';a++){
    count=0;
    k=0;
      for(int s=a;Y[s]!='\0';s++){
	for(int j=k;X[j]!='\0';j++){
	  if(X[j]==Y[s]){
	    //	    	    cout<<X[s];
	    count++;
	    k=j;
	    break;
	  }
	}
      }
      if(maxa[i]<count)maxa[i]=count;
    }
  }
  for(int i=0;i<n;i++){
    cout<<maxa[i]<<endl;
  }
  
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#define MAX_N 1001
using namespace std;
//lcs
int n,m;
string s,t;
int dp[MAX_N+1][MAX_N+1];
void solve(){
  for(int i=0;i<n;i++)
    for(int j=0;j<m;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]);
    }
  cout<<dp[n][m]<<endl;
}


int main(){
  int N;
  cin>>N;
  while(N--){
    cin>>s>>t;
    n=s.size();
    m=t.size();
    solve();
  }
  return 0;
}
//greatest common divisor
/*int main() {
  int a,b;
  cin >> a >>b;
  cout << __gcd(a,b)<<endl;
  return 0;
  }*/
//lcm
//__builtin_popcount()

//flymake
/*(require 'flymake)
 
(defun flymake-cc-init ()
(let* ((temp-file (flymake-init-create-temp-buffer-copy
'flymake-create-temp-inplace))
(local-file (file-relative-name
temp-file
(file-name-directory buffer-file-name))))
(list "g++" (list "-Wall" "-Wextra" "-fsyntax-only" local-file))))
 
(push '("\\.cpp$" flymake-cc-init) flymake-allowed-file-name-masks)
 
(add-hook 'c++-mode-hook
'(lambda ()
(flymake-mode t)))
(custom-set-variables
 '(ansi-color-names-vector ["#2d3743" "#ff4242" "#74af68" "#dbdb95" "#34cae2" "#008b8b" "#00ede1" "#e1e1e0"])
 '(custom-enabled-themes (quote (tsdh-light))))

*/

C++: #include <iostream>
#include <string>
#include <algorithm>

using namespace std;


static const int int N = 1000;


int lcs(string x, string y) {
    int c[N + 1][N + 1];
    int m = x.size();
    int n = y.size();
    int res = 0;

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

    for (int i = 0; i <= m; i++) c[i][0] = 0;
    for (int i = 0; i <= n; i++) c[0][i] = 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][j - 1], c[i - 1][j]);
            }
            res = max(res, c[i][j]);
        }
    }

    return 0;
}

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<string>
#include<cmath>
using namespace std;

int main(void){
  string st1, st2;
  int q, val[151][151];

  cin >> q;

  for(int i=0; i<q; i++){
    cin>>st1;
    cin>>st2;

    for(int j=0; j<=st1.length(); j++){
      for(int k=0; k<=st2.length(); k++){

	if(j==0 || k==0) val[j][k] = 0;
	else{
	  if(val[j-1][k] == min(st1.length(), st2.length())){
	    val[j][k] = st1.length();
	  }else{

	    if(st1[j-1] == st2[k-1]){
	      val[j][k] = val[j-1][k-1]+1;
	    }else{
	      val[j][k] = max(val[j-1][k], val[j][k-1]);
	    }
	  }
	}
      }
    }

    for(int j=0; j<=st1.length(); j++){
      for(int k=0; k<=st2.length(); k++){
	cout << val[j][k] << " ";
      }
      cout << "\n";
    }
    

    cout << val[st1.length()][st2.length()] << "\n";
  }

  return 0;
}