Go: ///
// File:  0528.go
// Author: ymiyamoto
//
// Created on Thu Mar 22 01:52:09 2018
//
package main

import (
	"bufio"
	"fmt"
	"os"
)

var S, T string
var dp [4001][4001]int

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	for {
		scanner.Scan()
		S = scanner.Text()
		if len(S) == 0 {
			return
		}

		scanner.Scan()
		T = scanner.Text()

		for i := range dp {
			for j := range dp[i] {
				dp[i][j] = 0
			}
		}

		dp[0][0] = 0
		for i := range S {
			for j := range T {
				if S[i] == T[j] {
					dp[i+1][j+1] = max(dp[i+1][j], max(dp[i][j+1], dp[i][j]+1))
				} else {
					dp[i+1][j+1] = 0
				}
			}
		}
		var m int
		for i := range dp {
			for j := range dp[i] {
				m = max(m, dp[i][j])
			}
		}
		fmt.Println(m)
	}
}

C++: #include<iostream>
 
using namespace std;
 
int solve(const string& s1, const string& s2, int l1, int l2){
  int tmp = 0;
  int res = 0;
  int len = min(s2.length()-l2,s1.length()-l1);
  for(int i = 0; i < len; i++){
    if(s1[l1+i] != s2[l2+i]){
      res = max(res,tmp);
      tmp = 0;
    }else{
      tmp++;
    }
  }
  return max(tmp,res);
}
 
int main(){
   
  string s1,s2;
  int l1,l2,ans;
  while(1) {
  	if(cin.eof()) {
  		break;
  	}
  	cin >> s1;
  	cin >> s2;
  	l1 = s1.length();
  	l2 = 0;
  	ans = 0;
  	while(l1 != 0 || l2 <= s2.length()) {

      if(l1 != 0){
      	l1--;
      } else {
      	l2++;
      }
      ans = max(ans,solve(s1,s2,l1,l2));
  	}
    cout << ans << endl;
  }
}

C++: #include <bits/stdc++.h>
using namespace std;
#define Rep(i,N) for(int i = 0; i < N; i++)
#define INF 1 << 28
typedef pair<int,int> Pi;
#define F first
#define S second
#define pb push_back

inline void chmax(int &a, int b) { a = max(a,b); }
inline void chmin(int &a, int b) { a = min(a,b); }

int main()
{
  int dp[4005][4005];
  string s, t;
  while(cin >> s >> t) {
    fill(dp[0],dp[4005],0);
    int ss = s.size(), ts = t.size();
    int maxv = 0;
    Rep(i,ts) {
      Rep(j,ss) {
	if(s[j] == t[i]) {
	  dp[i + 1][j + 1] = dp[i][j] + 1;
	  chmax(maxv,dp[i + 1][j + 1]);
	}
      }
    }
    cout << maxv << endl;
  }
  return 0;
}

C++: #include <string>
#include <iostream>
#include <algorithm>

using namespace std;

#define rep(i,n) for(i=0;i<n;i++)

unsigned short dp[4010][4010];

int main(){
  int i,j;
  string s,t;

  while(cin >> s >> t){
    int N=s.length(),M=t.length(),res=0;

    rep(i,4010) rep(j,4010) dp[i][j] = 0;
    rep(i,N) rep(j,M){
      if(s[i] == t[j]){
        dp[i+1][j+1] = dp[i][j] + 1;
        res = max(res, (int)dp[i+1][j+1]);
      } else {
        dp[i+1][j+1] = 0;
      }
    }

    cout << res << endl;
//    cout << dp[N][M] << endl;
  }

  return 0;
}

C++: #include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
typedef long long lint;

int main()
{
	char s[4096], t[4096];
	static int dp[2][4096];
	
	while (scanf("%s", s) == 1){
		scanf("%s", t);
		
		memset(dp, 0, sizeof(dp));
		
		int ans = 0;
		
		for (int i = 1; s[i - 1]; i++){
			for (int j = 1; t[j - 1]; j++){
				if (s[i - 1] == t[j - 1]) dp[i & 1][j] = max(dp[(i - 1) & 1][j - 1] + 1, max(dp[i & 1][j - 1], dp[(i - 1) & 1][j]));
				else dp[i & 1][j] = 0;
				ans = max(ans, dp[i & 1][j]);
			}
		}
		
		printf("%d\n", ans);
	}
	
	return (0);
}

C++: 
#include<iostream>
using namespace std;
int main()
{
  int ans,cnt;
  string s,t;
  while(cin>>s>>t){
    ans=0;
    for(int i=0;i<s.size();i++){
      cnt=0;
      for(int j=0;j<s.size()-i;j++){
	if(s[j+i]==t[j]){
	  cnt++;
	}else{
	  ans=max(ans,cnt);
	  cnt=0;
	}
      }
    }
    ans=max(ans,cnt);
    for(int i=0;i<t.size();i++){
      cnt=0;
      for(int j=0;j<t.size()-i;j++){
	if(t[i+j]==s[j]){
	  cnt++;
	}else{
	  ans=max(ans,cnt);
	  cnt=0;
	}
      }
    }
    ans=max(ans,cnt);
    cout<<ans<<endl;
  }
}

C++: # include <iostream>
# include <algorithm>
# include <vector>
# include <string>
# include <set>
# include <map>
# include <cmath>
# include <iomanip>
# include <functional>
# include <utility>
# include <stack>
# include <queue>
# include <list>
# include <tuple>
# include <unordered_map>
# include <numeric>
# include <complex>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
constexpr int INF = 2000000000;
constexpr int HINF = INF / 2;
constexpr double DINF = 100000000000000000.0;
constexpr long long LINF = 9223372036854775807;
constexpr long long HLINF = 4500000000000000000;
const double PI = acos(-1);
int dx[4] = { 0,1,0,-1 }, dy[4] = { 1,0,-1,0 };
# define ALL(x)     (x).begin(),(x).end()
# define UNIQ(c)    (c).erase(unique(ALL((c))), end((c)))
# define mp         make_pair
# define eb         emplace_back
# define FOR(i,a,b) for(int i=(a);i<(b);++i)
# define REP(i,n)   FOR(i,0,n)
# define INIT       std::ios::sync_with_stdio(false);std::cin.tie(0);


int main() {

	string s, t;
	while (cin >> s >> t) {
		int dp[4040][4040];
		for (int i = 1; i <= s.size(); i++) {
			for (int j = 1; j <= t.size(); j++) {
				if (s[i - 1] == t[j - 1]) {
					dp[i][j] = dp[i - 1][j - 1] + 1;
				}
			}
		}

		int ans = 0;
		for (int i = 0; i < s.size() + 1; i++) {
			for (int j = 0; j < t.size() + 1; j++) {
				ans = max(ans, dp[i][j]);
			}
		}
		cout << ans << endl;

		return 0;
	}
}

C++: //JOI 0528 Common Sub-String
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
	while(1){
		string s, t; int roop1=0, save=0, ans = 0;
		cin>>s;
		cin>>t;
		if(s==""){
		break;
		}
	for (int i = 0; i<s.size(); i++){
		for (int j = 0; j<t.size(); j++){
			if (s[i] == t[j]){
				roop1 = 0;
				save= 0;
				while (1){
					if (s[i + roop1] == 0 || t[j + roop1] == 0){
						break;
					}
					else{
						if (s[i + roop1] == t[j + roop1]){
							save += 1;
							roop1++;
						}
					else if (s[i + roop1] != t[j + roop1]){
							ans=max(ans,save);
							break;
						}
					}
				}
			}
		}
	}
	cout<<ans<<endl;
	}
	
	return 0;
}

C++: #include <algorithm>
#include <bitset>
#include <cstdio>
#include <cstring>
#include <cassert>
#include <cmath>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;

typedef long long LL;
typedef pair<int, int> P;
typedef pair<LL, LL> PLL;

int dp[4000][4000];
char s[4004], t[4004];

int main() {
    while (cin >> s >> t) {
        for (int j = 0; j < 4000; ++j) {
            fill(dp[j], dp[j] + 4000, 0);
        }

        int sLen = strlen(s);
        int tLen = strlen(t);

        int ret = 0;

        for (int j = 0; j < sLen; ++j) {
            for (int k = 0; k < tLen; ++k) {
                if (s[j] != t[k]) {
                    dp[j][k] = 0;
                } else if (j == 0 || k == 0) {
                    dp[j][k] = 1;
                } else {
                    dp[j][k] = dp[j-1][k-1] + 1;
                }

                ret = max(ret, dp[j][k]);
            }
        }

        cout << ret << endl;
    }
    return 0;
}