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 <algorithm>
#include<string.h>
using namespace std;
int LCS(char *x,char *y);
char x[1001], y[1001];
int lcs[1001][1001];
int main()
{
	int q,i,j;

	cin >> q;
	for (i = 0; i < q; i++) {
		cin >> x;
		cin >> y;
		cout << LCS(x, y) << endl;
	}
}

int LCS(char *x, char *y)
{
	int i, j;
	int len_x, len_y;
	len_x = strlen(x);
	len_y = strlen(y);
	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			lcs[i][j] = '\0';
		}
		//cout << endl;
	}
	i = 0;
	while (x[i] != y[0]) {
		lcs[i][0] = 0;
		i++;
		if (i == len_x) break;

	}
	for (j = i; j < len_x; j++) {
		lcs[j][0] = 1;
	}
	while (y[i] != x[0]) {
		lcs[0][i] = 0;
		i++;
		if (i == len_y) break;
	}
	for (j = i; j < len_y; j++) {
		lcs[0][j] = 1;
	}

	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			if (x[i] == y[j]) {
				lcs[i][j] = lcs[i - 1][j - 1] + 1;
				//printf("lcs[%d][%d]=%d\n", i, j, lcs[i - 1][j - 1] + 1);
			}
			if (x[i] != y[j]) {
				lcs[i][j] = max(lcs[i - 1][j], lcs[i][j - 1]);
				//printf("lcs[%d][%d]=%d\n", i, j, max(lcs[i - 1][j], lcs[i][j - 1]));
			}
		}
	//cout << endl;

	}
	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			//printf("%d ", lcs[i][j]);
		}
		//cout << endl;
	}
	//cout << "len_x=" << len_x << endl << "len_y=" << len_y << endl;
			
	return lcs[i-1][j-1];
}

C++: // input: alds1_10_c.in
#include<iostream>
using namespace std;

bool x[26], y[26];

int lcs(string& a, string& b) {
  for(int i=0; i<26; i++) {
    x[i] = 0;
    y[i] = 0;
  }

  for(int i=0; i<a.size(); i++) {
    x[a.c_str()[i] - 97] = true;
  }

  for(int i=0; i<b.size(); i++) {
    y[b.c_str()[i] - 97] = true;
  }

  int n = 0;
  for(int i=0; i<26; i++) {
    if(x[i] && y[i])
      n++;
  }

  return n;
}

int main() {
  int n;
  string a, b;
  cin >> n;
  for(int i=0; i<n; i++) {
    cin >> a >> b;

    cout << lcs(a, b) << endl;
  }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <stdint.h>
#include <queue>
#include <bitset>
#include <iomanip>
#include <set>
#include <map>

using namespace std;

#define PI (3.14159265358979323846)
#define INF (2147483647)
#define INF_LL (9223372036854775807)
#define DIV_NUM (1000000007)

// 配列初期化テンプレ
template<typename A, size_t N, typename T>
void Fill(A(&array)[N], const T& val) {
	std::fill((T*)array, (T*)(array + N), val);
}


// 最長共通部分列

// dp[決めた桁数][未満フラグ][1を含んでいたか否かフラグ]
#define MAX_LENGTH_S1 (1000)
#define MAX_LENGTH_S2 (1000)
// dp[i][j]:S1[i]までとS2[j]までの最長共通部分列
long long dp[MAX_LENGTH_S1 + 1][MAX_LENGTH_S2 + 1];

int main() {

	int set_num;
	cin >> set_num;
	for (int num = 0; num < set_num; num++) {

		string S1, S2;
		cin >> S1 >> S2;
		int len1 = S1.size();
		int len2 = S2.size();

		dp[0][0] = 0;
		for (int i = 0; i < len1; i++) {
			for (int j = 0; j < len2; j++) {
				if (S1[i] == S2[j]) dp[i + 1][j + 1] = max(dp[i][j] + 1, max(dp[i + 1][j], dp[i][j + 1]));
				else dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
			}
		}
		int LCS_length = dp[len1][len2];
		cout << LCS_length << endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;
using ll = long long;
int INF = 1000000009;
int lcs(string s,string t){
    int l = s.size(),r = t.size();
    s += '#';
    t += '=';
    vector<vector<int>> dp(l+2,vector<int>(r+2,-(l+r)));
    dp[0][0] = 0;
    rep(i, l+1)
    {
        rep(j, r+1)
        {
            if(dp[i+1][j]<dp[i][j])dp[i+1][j]=dp[i][j];
            if(dp[i][j+1]<dp[i][j])dp[i][j+1]=dp[i][j];
            if(dp[i+1][j+1]<(dp[i][j]+(s[i]==t[j])))dp[i+1][j+1]=dp[i][j]+(s[i]==t[j]);
        }
    }
    return dp[l][r];
}
int main()
{
    int n;
    string s, t;
    cin >> n;
    vector<int> ans;
    rep(i, n)
    {
        cin >> s >> t;
        ans.push_back(lcs(s, t));
    }
    rep(i,n){
        cout << ans[i] << endl;
    }
}

C++: #include <iostream>
#include <algorithm>
#include <string>
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(void) {
  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>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = 1001001001;
const int MOD = 1000000007;

template <typename T>
void print(const T &v);

int main()
{
    int n;
    cin >> n;
    for (int k = 0; k < n; k++)
    {
        string A, B;
        cin >> A >> B;
        int a = A.size();
        int b = B.size();
        vector<vector<int>> dp(b + 1, vector<int>(a + 1, 0));
        for (int i = 0; i < b; i++)
        {
            for (int j = 0; j < a; j++)
            {
                if (B[i] == A[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[b][a] << endl;
    }
    return 0;
}

// Use For Debug
template <typename T>
void print(T const &v)
{
    for (int i = 0; i < v.size(); i++)
    {
        if (i)
            cout << ' ';
        cout << v[i];
    }
    cout << 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;
}