Go: package main

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

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// if S[i-1] == T[j-1] {
				// 	dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				// } else {
				// 	dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				// }
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: #include <algorithm>
#include <complex>
#include <cstdlib>
#include <ctime>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;
#define SAY_YES cout << "YES" << endl;
#define SAY_Yes cout << "Yes" << endl;
#define SAY_NO cout << "NO" << endl;
#define SAY_No cout << "No" << endl;
#define IFYES(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "YES" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "NO" << endl;  \
    }
#define IFYes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "Yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "No" << endl;  \
    }
#define IFyes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "no" << endl;  \
    }
#define DEBUG_OUTPUT_ARRAY(XXX, ONE)                            \
    for (int i = 0; i < (ONE); i++)                             \
    {                                                           \
        cout << "DEBUG: i = " << i << " -> " << XXX[i] << endl; \
    }
#define DEBUG_OUTPUT_ARRAY2(XXX, ONE, TWO)                             \
    for (int i = 0; i < (ONE); i++)                                    \
    {                                                                  \
        cout << "<<< i = " << i << " >>>" << endl;                     \
        for (int j = 0; j < (TWO); j++)                                \
        {                                                              \
            cout << "DEBUG: j = " << j << " -> " << XXX[i][j] << endl; \
        }                                                              \
    }
#define DEBUG_OUTPUT_ARRAY2_BOX(XXX, ONE, TWO) \
    for (int i = 0; i < (ONE); i++)            \
    {                                          \
        cout << i << "  ";                     \
        for (int j = 0; j < (TWO); j++)        \
        {                                      \
            cout << XXX[i][j] << " ";          \
        }                                      \
        cout << endl;                          \
    }

typedef pair<long long int, long long int> pll;


const long long int mod = 1000000007;
const long long int INF = 99999999999999999;



class LCS{
    public:
    long long int **dp;
    long long int **longest;
    long long int result;
    string LCSstr;
    LCS(long long int one,long long int two){
        dp=new long long int*[one];
        longest=new long long int *[one];
        for(int i=0;i<one;i++){
            dp[i]=new long long int[two];
            longest[i]=new long long int[two];
        } 
    }
    void DoLCS(string str1,string str2){
        LCSstr.clear();
        for(int i=0;i<str1.length();i++){
            for(int j=0;j<str2.length();j++){
                dp[i][j]=0;
                longest[i][j]=0;
            }
            
        }

        for(int i=0;i<str1.length();i++){
            if(str1[i]==str2[0]){dp[i][0]=1;}
            else{dp[i][0]=0;}
            for(int j=1;j<str2.length();j++){
                if(i!=0)dp[i][j]=longest[i-1][j-1];
                if(str1[i]==str2[j]){dp[i][j]++;}
            }
            
            if(i!=0){
                longest[i][0]=max({longest[i-1][0],dp[i][0]});
                for(int j=1;j<str2.length();j++){
                    longest[i][j]=max({longest[i-1][j],dp[i][j],longest[i][j-1]});
                }
            }else{
                longest[0][0]=dp[i][0];
                for(int j=1;j<str2.length();j++){
                    longest[0][j]=max({dp[0][j],longest[0][j-1]});
                }
            }
        }

        pair<long long int ,long long int>rev;
        rev={str1.length(),str2.length()};
        long long int now=longest[str1.length()-1][str2.length()-1];
        bool key=false;
        //cout<<now<<endl;
        //DEBUG_OUTPUT_ARRAY2_BOX(dp,rev.first,rev.second);
        while(now!=0){
            key=false;
            for(int j=0;j<rev.first;j++){
                if(now==dp[j][rev.second-1]&&(now-1==longest[max(j-1,0)][max(rev.second-1-1,0LL)]||j==0||rev.second-1==0)){
                    
                    LCSstr.push_back(str1[j]);
                    rev={j,rev.second-1};
                    now--;
                    key=true;
                    //cout<<"REV>>"<<rev.first<<" "<<rev.second<<endl;
                    break;
                }
            }
            if(key){continue;}
            for(int j=0;j<rev.second;j++){
                if(now==dp[rev.first-1][j]&&(now-1==longest[max(rev.first-1-1,0LL)][max(j-1,0)]||rev.first-1==0||j==0)){
                    now--;
                    LCSstr.push_back(str2[j]);
                    rev={rev.first-1,j};
                    key=true;
                    
                    //cout<<"REV>>"<<rev.first<<" "<<rev.second<<endl;
                    break;
                }
            }
            if(!key){
                rev={rev.first-1,rev.second-1};
            }        
        }
        reverse(LCSstr.begin(),LCSstr.end());
        result=LCSstr.length();
    }
    ~LCS(){}
};

long long int N,M,W,dp[55000]={},c[10005],w[105];
string str[350],str2[350];

int main()
{
    cout << fixed << setprecision(18);
    cin>>N;
    
    LCS lcs(1005,1005);
    for(long long int i = 1; i <= N; i++){
        cin>>str[i]>>str2[i];
        

        lcs.DoLCS(str[i],str2[i]);
        cout<<lcs.LCSstr.length()<<endl;
        
    }
     
        
        
    
    
}