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<math.h>
#include<limits.h>
#include<iostream>
#include<string>
#include<vector>
#include<stdio.h>
#include<sstream>
#include<list>
#include<queue>
#include<algorithm>
#include<functional>
#include<map>
#include<set>
#include<utility>
#include<initializer_list>
#include<tuple>
#include<regex>
using namespace std;
#define ull unsigned long long
#define ll long long
#define rep(i, n) for(int i=0;i<(int)(n);i++)
#define all(t) t.begin(), t.end()
bool isSubstring(string substr, string t) {
	int n = substr.length();
	int seek = 0;
	rep(i, n) {
		bool ex = 0;
		for (int j = seek; j < t.length(); j++) {
			if (substr[i] == t[j]) {
				ex = 1;
				seek = j + 1;
				break;
			}
		}
		if (ex) {
			continue;
		}
		else {
			return false;
		}
	}
	return true;

}

int LongestCommonSubstring(string s, string t) {
	vector<int>dp(s.length(), 0);
	int n = s.length();
	string lcs = "";
	if (isSubstring(s.substr(n - 1, n), t)) {

		dp[n - 1] = 1;
		lcs = s[n - 1];
	}
	for (int i = n - 2; i >= 0; i--) {
		//string substr = s.substr(i, n);
		string substr = s[i] + lcs;
		int issubst = isSubstring(substr, t);
		if (issubst) lcs = substr;
		dp[i] = dp[i + 1] + issubst;
	}
	return dp[0];
}
int main() {
	//cout << isSubstring("abc", "abcde") << endl;
	//cout << isSubstring("bd", "abcde") << endl;
	//cout << isSubstring("db", "abcde") << endl;

	//cout << LongestCommonSubstring("bacd", "becd") << endl;
	//cout << LongestCommonSubstring("abcd", "becd") << endl;
	int q;
	cin >> q;
	vector<string> s(q);
	vector<string> t(q);
	rep(i, q) {
		cin >> s[i] >> t[i];
	}
	rep(i, q) {
		cout << LongestCommonSubstring(s[i], t[i]) << endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); i++)
using ll = long long;
using P = pair<int, int>;
#include<algorithm>

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; // X[0]に空白を挿入
    Y = ' ' + Y; // Y[0]に空白を挿入
    for (int i = 0; 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 <iostream>
#include <string>
#include <cstring>
using namespace std;

int q;
int **len;
int common(string a,string b,int m,int n){
    if(m==0||n==0){
        return 0;
    }
    if(a[m-1]==b[n-1]){
        if(m>1&&n>1){
            if(len[m-2][n-2]!=-1)len[m-1][n-1]=len[m-2][n-2]+1;
            else len[m-1][n-1]=common(a.substr(0,m-1),b.substr(0,n-1),m-1,n-1)+1;
        }else{
            len[m-1][n-1]=1;
        }
    }
    else{
        int l1,l2;
        //?±?l1
        if(n>1){
            if(len[m-1][n-2]!=-1)l1=len[m-1][n-2];
            else l1=len[m-1][n-2]=common(a,b.substr(0,n-1),m,n-1);
        }else l1=-1;
        if(m>1){
            if(len[m-2][n-1]!=-1)l2=len[m-2][n-1];
            else l2=len[m-2][n-1]=common(a.substr(0,m-1),b,m-1,n);
        }else l2=-1;

        len[m-1][n-1]=max(l1,l2);
    }
    return len[m-1][n-1];
}

int main()
{
    cin>>q;
    int i;
    for(i=0;i<q;i++){
        string a,b;
        cin>>a>>b;
        int m=a.length();
        int n=b.length();
        len=new int*[m];
        int j;
        for(j=0;j<m;j++){
            len[j]=new int[n];
            memset(len[j],-1,n*sizeof(int));
        }
        cout<<common(a,b,m,n)<<endl;
    }
    return 0;
}

//int main(){
//    int **p=new int*[5];
//    p[1]=new int[5];
//    memset(p[1],-1,5*sizeof(int));
//    cout<<p[1][3]<<" "<<p[0][1];
//}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
const int MAX = 1000;
int c[MAX + 1][MAX + 1];
int lcs(string x, string y)
{
	int m = x.length();
	int n = y.length();
	int maxLen = 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]);
			maxLen = max(maxLen, c[i][j]);
		}
	return maxLen;
}
int main()
{
	int n;
	(cin >> n).get();
	for (int i = 0; i < n; i++)
	{
		string x, y;
		getline(cin, x);
		getline(cin, y);
		cout << lcs(x, y) << endl;
	}
}

C++: #include<stdio.h>

int strlen(char s[]) {
  int w = 0;
  while (1) {
    if (s[w] == '\0')
      break;
    w++;
  }
  return w;
}

int max(int a, int b, int c){
  int m = a;
  if (m < b)
    m = b;
  if (m < c)
    m = c;
  return m;
}

int main(void){
  int q, xl = 0, yl = 0, h = 0, i = 0, j = 0;
  int d, ans = 0;
  int DP[1001][1001];
  char X[1001], Y[1001];

  for (i = 0; i < 1001; i++) {
    DP[i][0] = 0;
  }
  for (i = 0; i < 1001; i++) {
    DP[0][i] = 0;
  }

  scanf("%d", &q);
  for (h = 0; h < q; h++) {

    scanf("%s", X);
    scanf("%s", Y);
    xl = strlen(X);
    yl = strlen(Y);
    //printf("xl:%d, yl:%d\n", xl, yl);

    for (i = 1; i <= xl; i++) {
       for (j = 1; j <= yl; j++) {
        if (X[i-1] == Y[j-1])
          d = 1;
        else
          d = 0;
        DP[i][j] = max(DP[i-1][j-1], DP[i-1][j], DP[i-1][j]) + d;
        if(DP[i][j] > ans)
          ans = DP[i][j];
      }
    }
    printf("%d\n", ans);
    ans = 0;
  }
  return 0;
}

C++: #include<cstdio>
#include<stdlib.h>
#include<iostream>
using namespace std;

const int maxn = 1005;

int T[maxn][maxn];

int calculateCommon(string s1,string s2){
	for(int i = 0;i <= s1.length();i++){
		for(int j = 0;j <= s2.length();j++){
			if(i == 0 || j == 0){
				T[i][j] = 0;
			}else{
				if(s1[i - 1] == s2[j - 1]){
					T[i][j] = T[i - 1][j - 1] + 1;
				}else{
					T[i][j] = (T[i][j - 1] < T[i - 1][j]) ? T[i - 1][j]:T[i][j - 1];
				}
			}
	//		cout << "T[" << i << "][" << j << "] = " << T[i][j] << endl;
		}
	}
	return T[s1.length()][s2.length()];
}

int main(){
	int q;
	string s1;
	string s2;
	cin >> q;
	getchar();
	for(int i = 0;i < q;i++){
		getline(cin,s1);
		getline(cin,s2);
		cout << calculateCommon(s1,s2) << endl;
	}
}