Codeforces 501B - Misha and Changing Handles (STL)

题意

思路

代码

#include <cstdio>

#include <stack>

#include <list>

#include <set>

#include <iostream>

#include <string>

#include <vector>

#include <queue>

#include <functional>

#include <cstring>

#include <iomanip>

#include <algorithm>

#include <cctype>

#include <string>

#include <map>

#include <cmath>

using namespace std;

#define LL long long

#define ULL unsigned long long

#define SZ(x) (int)x.size()

#define Lowbit(x) ((x) & (-x))

#define MP(a, b) make_pair(a, b)

#define MS(arr, num) memset(arr, num, sizeof(arr))

#define PB push_back

#define F first

#define S second

#define ROP freopen("input.txt", "r", stdin);

#define MID(a, b) (a + ((b - a) >> 1))

#define LC rt << 1, l, mid

#define RC rt << 1|1, mid + 1, r

#define LRT rt << 1

#define RRT rt << 1|1

#define BitCount(x) __builtin_popcount(x)

#define BitCountll(x) __builtin_popcountll(x)

#define LeftPos(x) 32 - __builtin_clz(x) - 1

#define LeftPosll(x) 64 - __builtin_clzll(x) - 1

const double PI = acos(-1.0);

const int INF = 0x3f3f3f3f;

const double eps = 1e-8;

const int MAXN = 1000 + 10;

const int MOD = 1000007;

const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };

typedef pair<int, int> pii;

typedef vector<int>::iterator viti;

typedef vector<pii>::iterator vitii;

vector<string> ans;

set<string> st;

map<string, string> mp;

int main()

{

// ROP;

int n, i, j;

cin >> n;

for (i = 0; i < n; i++)

{

string from, to;

cin >> from >> to;

st.insert(to);

if (!st.count(from)) ans.PB(from);

mp[from] = to;

}

cout << SZ(ans) << endl;

for (i = 0; i < SZ(ans); i++)

{

string tmp = ans[i];

while (mp.count(mp[tmp])) tmp = mp[tmp];

cout << ans[i] << " " << mp[tmp] << endl;

}

return 0;

}