Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	Q := sc.nextInt()
	for q := 0; q < Q; q++ {
		X, Y := sc.nextStr(), sc.nextStr()
		xLen, yLen := len(X), len(Y)
		dp := make([][]int, xLen+1)
		for i := 0; i <= xLen; i++ {
			dp[i] = make([]int, yLen+1)
		}
		for x := 0; x <= xLen; x++ {
			for y := 0; y <= yLen; y++ {
				if x == 0 || y == 0 {
					dp[x][y] = 0
				} else if X[x-1] == Y[y-1] {
					dp[x][y] = dp[x-1][y-1] + 1
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1])
				}
			}
		}
		fmt.Fprintln(wtr, dp[xLen][yLen])
	}

	wtr.Flush()
}

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

static const int N = 1000;
int lcs(string,string);

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;
}

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;
  Y = ' ' + Y;
  for(int i=0;i<=m;i++) c[i][0] = 0;
  for(int j=0;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;
}

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;
	Y = ' ' + Y;
	for (int i = 0; i <= m; i++) c[i][0] = 0;
	for (int j = 0; 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<string>
int main()
{
  int n;
  int an[1000];
  int l=0;
  std::cin>>n;
  std::string x;
  std::string y;
  int ans[1001][1001];
  int j,k;
  for(int i=0;i<n;i++){
    std::cin>>x;
    std::cin>>y;
    for(int j=0;j<=1000;j++){
      for(int k=0;k<=1000;k++){
	ans[j][k]=0;
      }
    }
    for(int j=0;j<=x.size();j++){
      for(int k=0;k<=y.size();k++){
	if(x[j]==y[k]){
	  ans[j][k]=ans[j-1][k-1]+1;
	}else{
	  if(ans[j][k-1]>ans[j-1][k]){
	    ans[j][k]=ans[j][k-1];
	  }else{
	    ans[j][k]=ans[j-1][k];
	  }
	}
      }
    }
    std::cout<<ans[x.size()-1][y.size()-1]<<'\n';  
  }
  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] = max(val[j-1][k], val[j][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;
}

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

// macro
#define rep(i,n) for(i=0;i<n;i++)
#define ll long long
#define all(v) v.begin(), v.end()

// code starts
#define INF 10000000

int main()
{
  int q;cin>>q;
  int i,j,k;
  rep(i,q)
  {
    string x,y;cin>>x>>y;
    int xs=x.size();
    int ys=y.size();
    vector<vector<int>> dp(xs+1,vector<int>(ys+1,0));
    rep(j,xs)
    {
      rep(k,ys)
      {
        if(x[j]==y[k])
        {
          dp[j+1][k+1]=dp[j][k]+1;
        }
        else
        {
          dp[j+1][k+1]=max(dp[j][k+1],dp[j+1][k]);
        }
      }
    }
    cout<<dp[xs][ys]<<endl;
  }
}

C++: #include<bits/stdc++.h>
using namespace std;
#define inf 1e9
#define ll long long
#define ull unsigned long long
#define M 1000000007
#define P pair<int,int>
#define PLL pair<ll,ll>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
#define IN(n,a) rep(i,n){ cin>>a[i]; }
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define PI 3.14159265


void f(){
  string x,y;
  cin>>x>>y;
  int dp[1100][1100]={};
  
  rep(i,x.length()+1){
    rep(j,y.length()+1){
      if(i==0||j==0) continue;
      if(x[i-1]==y[j-1]) dp[i][j]=dp[i-1][j-1]+1;
      else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        
      
    }
  }

  cout<<dp[(int)x.length()][(int)y.length()]<<endl;
}


int main(){
  int q;
  cin>>q;
  while(q--){
    f();
  }
}

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

int main() {
  int q;
  cin >> q;
  for (int i=0;i<q;++i) {
    string str1,str2;
    cin >> str1 >> str2;
    int size1 = str1.size();
    int size2 = str2.size();
    int matrix[size1+1][size2+1];
    for (int j=0;j<=size1;++j)
      matrix[j][0] = 0;
    for (int j=0;j<=size2;++j)
      matrix[0][j] = 0;
    for (int j=0;j<=size1;++j) {
      for (int k=0;k<=size2;++k) {
	if (j<=0||k<=0) {
	  matrix[j][k] = 0;
	}
	else if (str1[k]==str2[j]) {
	  matrix[j][k] = 1 + matrix[j-1][k-1];
	}
	else {
	  matrix[j][k] = max(matrix[j][k-1],matrix[j-1][k]);
	}
      }
    }
    cout << matrix[size1][size2] << endl;
  }
}

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