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>
using namespace std;
int main(void){
    int n;
    cin >> n;
    for(int i = 0;i < n;i++){
        string X,Y;
        cin >> X >> Y;
        int L[X.length()+10][Y.length()+10];
        for(int j = 0;j < X.length()+5;j++){
            for(int k = 0;k < Y.length()+5;k++){
                L[j][k] = 0;
            }
        }
        for(int j = 1;j<=X.length();j++){
            for(int k = 1;k<=Y.length();k++){
                if(Y[k-1] == X[j-1]){
                    L[j][k] = 1+L[j-1][k-1];
                }
                else{
                    L[j][k] = max(L[j-1][k],L[j][k-1]);
                }
            }
        }
        cout << L[X.length()][Y.length()] << endl;
    }
    return 0;
}

C++: #include "iostream"
#include "string.h"

using namespace std;

int L[1001][1001];

int lcs( char s1[], char s2[], int l1, int l2 ) {

	if (L[l1][l2] != 0)return L[l1][l2];

	if (l1 == 0 || l2 == 0) return 0;
	else if (s1[l1-1] == s2[l2-1]) L[l1][l2] = lcs(s1, s2, l1 - 1, l2 - 1) + 1;
	else {
		int lsc1 = lcs(s1, s2, l1 - 1, l2);
		int lsc2 = lcs(s1, s2, l1, l2 - 1);

		if (lsc1 > lsc2) L[l1][l2] = lsc1;
		else L[l1][l2] = lsc2;
	}

	return L[l1][l2];
}

int main() {

	int n;
	char s1[1000], s2[1000];

	cin >> n;

	int ans[150];

	for (int i = 0; i < n; i++) {
		cin >> s1;
		cin >> s2;

		ans[i] = lcs(s1, s2, strlen(s1), strlen(s2));

		for (int j = 0; j < strlen(s1); j++) {
			for (int k = 0; k < strlen(s2); k++) {
				L[j][k] = 0;
			}
		}
	}

	for (int i = 0; i < n; i++) {
		cout << ans[i] << endl;
	}

	return 0;
}

C++: #include <cstdio>
#include <cstdint>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <array>
#include <vector>
#include <unordered_map>

int lcs(const std::string& x, const std::string& y)
{
    int c[x.size()][y.size()] = {0};
    for (int i = 0; i < x.size(); ++i) {
        for (int j = 0; j < y.size(); ++j) {
            if (i == 0) {
                if (j == 0) {
                    if (x[i] == y[j]) {
                        c[i][j] = 1;
                    } else {
                        c[i][j] = 0;
                    }
                } else {
                    if (x[i] == y[j]) {
                        c[i][j] = 1;
                    } else {
                        c[i][j] = c[i][j-1];
                    }
                }
            } else if (j == 0) {
                if (i == 0) {
                    if (x[i] == y[j]) {
                        c[i][j] = 1;
                    } else {
                        c[i][j] = 0;
                    }
                } else {
                    if (x[i] == y[j]) {
                        c[i][j] = 1;
                    } else {
                        c[i][j] = c[i-1][j];
                    }
                }
            } else {
                if (x[i] == y[j]) {
                    c[i][j] = c[i-1][j-1] + 1;
                } else {
                    c[i][j] = std::max(c[i][j-1], c[i-1][j]);
                }
            }
        }
    }

    return c[x.size() -1][y.size()-1];
}

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

    std::string x;
    std::string y;
    for (int i = 0; i < n; ++i) {
        std::cin >> x >> y;
        std::cout << lcs(x, y) << std::endl;
    }

    return 0;
}

C++: #include <iostream>

using namespace std;

int lcs(string X, string Y) {
  int memo[1010][1010];
  int maxl = 0;
  int k = 0;
  for (int i = 0; i < X.size(); i++) {
    for (int j = 0; j < Y.size(); j++) {
      if (i <= 0 || j <= 0) {
        if (X[i] == Y[j]) {
          memo[i][j] = 1;
        } else {
          memo[i][j] = 0;
        }
      }
      else {
        if (X[i] == Y[j]) {
          memo[i][j] = memo[i-1][j-1] + 1;
        } else {
          memo[i][j] = max(memo[i-1][j], memo[i][j-1]);
        }
      }
      maxl = max(maxl, memo[i][j]);
      //cout << i << "," << j << "," << X[i] << "," << Y[j] << "," << maxl << endl;
    }
  }
  return maxl;
}

int main() {
  int q; cin >> q;
  for (int i = 0; i < q; i++) {
    string X, Y; cin >> X >> Y;
    cout << lcs(X, Y) << endl;
  }
}

C++: #include <stdio.h>
#include <string>
#include <iostream>
#include <algorithm>

using namespace std;

//I can't understand,so I imitated yutaka watabe's book.
//I think this problem has 5 star rank difficulty.

void calc(char X[],char Y[]){
	int X_length=0,Y_length=0;
	int table[1001][1001];
	for(int i = 0; i < 1001; i++){
		for(int k = 0; k < 1001; k++)table[i][k] = 0;
	}
	for(int i = 0; X[i] != '\0'; i++)X_length++;
	for(int i = 0; Y[i] != '\0'; i++)Y_length++;
	int max_succeed = 0;
	for(int i = 0; i < X_length; i++){
		for(int k = 0; k < Y_length; k++){
			if(X[i] == Y[k]){
				table[i+1][k+1] = table[i][k] + 1;
			}else{
				table[i+1][k+1] = max(table[i+1][k],table[i][k+1]);
			}
			max_succeed = max(max_succeed,table[i+1][k+1]);
		}
	}
	printf("%d\n",max_succeed);
}

int main(){
	int q;
	char X[1001],Y[1001];
	scanf("%d",&q);
	for(int i=0;i<q;i++){
		scanf("%s %s",X,Y);
		calc(X,Y);
	}
    return 0;
}