Codeforces Round #436 (Div. 2)

题目：http://codeforces.com/contest/864
A.Fair Game
题意：两人将卡片拿光，且数量相等

The game is considered fair if Petya and Vasya can take all n cards, and the number of cards each player gets is the same.

代码：

#include<bits/stdc++.h>using namespace std;map<int,int> mp;map<int,int>::iterator one,two;int main(){    int n,x;    cin >> n;    for(int i = 0;i < n;i++)        cin >> x,mp[x]++;    one = mp.begin();    two = ++mp.begin();    if(mp.size() == 2 && one->second == two->second)        printf("YES\n%d %d\n",one->first,two->first);    else        printf("NO\n");    return 0;}

B.Polycarp and Letters
题意：pos为小写字母的位置，且字母中间是小写字母，即求最长的连续不同字母小写字母数
代码：

#include<bits/stdc++.h>using namespace std;char s[205];map<int,int> mp;int main(){    int n,x;    cin >> n;    cin >> s;    int maxn = 0,tmp = 0;    for(int i = 0;i < n;i++)    {        if(s[i] >= 'a' && s[i] <= 'z')        {            if(mp[s[i]] == 0)                tmp++;            mp[s[i]]++;        }        else        {            maxn = max(maxn,tmp);            tmp = 0;            mp.clear();        }    }    if(tmp)        maxn = max(maxn,tmp);    cout << maxn << "\n";    return 0;}

C.Bus
题意：一趟来回定义为从0到a，或者从a到0，f位置有一个加油站，让你跑k次来回，求加油数（油箱容量b）
代码：

#include<bits/stdc++.h>using namespace std;int main(){    int a,b,f,k;    cin >> a >> b >> f >> k;    int st,ed;    int cur = b,ans = 0;    for(int i = 1;i <= k;i++)    {        if(i&1)            st = 0,ed = a;        else            st = a,ed = 0;        if(cur < abs(f-st)) cur = b,ans++;        if(cur < abs(f-st)) return 0 * printf("-1\n");        cur -= abs(f-st);        if(i != k)//不是最后一趟        {            if(cur < abs(ed-f)*2) cur = b,ans++;            if(cur < abs(ed-f)*2) return 0 * printf("-1\n");            cur -= abs(ed-f);        }        else        {            if(cur < abs(ed-f)) cur = b,ans++;            if(cur < abs(ed-f)) return 0 * printf("-1\n");            cur -= abs(ed-f);        }    }    cout << ans << "\n";    return 0;}

D.Make a Permutation!
题意：给你一个数列（1~n），你可以操作一个数，最后使得成为1~n的全排列，求最小操作数
代码：

#include<bits/stdc++.h>using namespace std;const int N = 200005;int a[N],cnt[N],v[N],vis[N];int main(){    ios_base::sync_with_stdio(0);cin.tie(0);    int n;    cin >> n;    for(int i = 1;i <= n;i++)        cin >> a[i],cnt[a[i]]++;    int num = 0;    for(int i = 1;i <= n;i++)        if(cnt[i] == 0)            v[++num] = i;    int p = 1;    for(int i = 1;i <= n;i++)    {        if(cnt[a[i]] > 1)        {            if(v[p] < a[i] || vis[a[i]])                cnt[a[i]]--,a[i] = v[p],p++;            else                vis[a[i]] = 1;        }    }    cout<<num<<"\n";    cout<<a[1];    for(int i = 2;i <= n;i++)        cout<<" "<<a[i];    cout<<"\n";    return 0;}

E.Fire
题意：失火了，有n个文件，保存文件需要t时间，文件会在d时间被摧毁，求最多能得到最大价值的文件
思路：dp……