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 <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int kMax = 1000 + 10;

char a_str[kMax], b_str[kMax];
int dp[kMax][kMax];

int main() {
    int q;
    scanf("%d", &q);
    while(q --) {
        scanf("%s%s", a_str, b_str);
        int n = strlen(a_str), m = strlen(b_str);
        for(int i = 0;i < n;++ i) {
            for(int j = 0;j < m;++ j) {
                if(a_str[i] == b_str[j]) dp[i][j] = (i && j ? (dp[i-1][j-1] + 1) : 1);
                else dp[i][j] = max(i ? dp[i-1][j] : 0, j ? dp[i][j-1] : 0);
            }
        }
        printf("%d\n", dp[n-1][m-1]);
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int LCS(string &X, string &Y) {
  X = " " + X;
  Y = " " + Y;
  int X_size = X.size(), Y_size = Y.size();
  vector<vector<int>> CS(Y_size, vector<int>(X_size, 0));
  for (int i = 0; i < Y_size; i++) {
    for (int j = 0; j < X_size; j++) {
      if (i == 0 || j == 0) continue;
      else if (X[j] == Y[i]) {
        CS[i][j] = CS[i - 1][j - 1] + 1;
      } else {
        CS[i][j] = max(CS[i][j - 1], CS[i - 1][j]);
      }
    }
  }
  return CS[Y_size - 1][X_size - 1];
}
int main() {
  int q;
  cin >> q;
  string X, Y;
  for (size_t i = 0; i < q; i++) {
    cin >> X >> Y;
    cout << LCS(X, Y) << endl;

    X.clear();
    Y.clear();
  }
}

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

int dp[1005][1005];
int q,n,m;
string x,y;

int main() {
	cin >> q;
	for(int a = 0; a < q; a++){
		cin >> x >> y;
		n = x.size();
		m = y.size();
		for(int i = 0; i < n; i++){
			for(int j = 0; j < m; j++){
			if		(x[i] == y[j]) dp[i+1][j+1] = dp[i][j] + 1;
			else if (x[i] != y[j]) dp[i+1][j+1] = max(dp[i][j+1],dp[i+1][j]);
			}
		}
		cout << dp[n][m] << endl;
	}
}

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=1;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 <bits/stdc++.h>
using namespace std;

int main(){
        int q;
        cin >> q;
        for(int k = 0; k < q; k++){
                string x, y;
                cin >> x >> y;
                int n = x.size(), m = y.size();
                int l[n + 1][m + 1];
                for(int j = 0; j <= m; j++){
                        for(int i = 0; i <= n; i++){
                                if(i == 0 || j == 0) l[i][j] = 0;
                                else if(x[i - 1] == y[j - 1]) l[i][j] = 1 + l[i - 1][j - 1];
                                else l[i][j] = max(l[i - 1][j], l[i][j - 1]);
                        }
                }
                cout << l[n][m] << endl;
        }
        return 0;
}

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

using namespace std;

int main(void) {
	int noq,nmax,res;
	cin >> noq;
	string t1,t2,X,Y;
	for (int q = 0; q < noq; ++q) {
		cin >> t1 >> t2;
		if (t1.length() < t2.length()) {
			X = t2;
			Y = t1;
		}
		else {
			X = t1;
			Y = t2;
		}
		vector<int> dp(X.length(),0);
		for (int i = 0; i < Y.length(); ++i) {
			nmax = 0;
			for (int j = 0; j < X.length(); ++j) {
				if (Y[i] == X[j]) {
					if (nmax+1 > dp[j]) {
						dp[j] = nmax+1;
					}
					else {
						nmax = max(dp[j],nmax);
					}
				}
				else {
					if (dp[j] < nmax) {
						dp[j] = nmax;
					}
					else {
						nmax = dp[j];
					}
				}
			}
		}
		res = 0;
		for (int i = 0; i < X.length(); ++i) {
			res = max(dp[i],res);
		}
		cout << res << endl;
	}
	return 0;
}