Educational Codeforces Round 9

DUANG: http://codeforces.com/contest/632

A

倒着推

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
    int n, m;
    cin >> n >> m;
    stack<string> s;
    while(!s.empty()) s.pop();
    for(int i = 0; i < n; ++i){
        string ss;
        cin >> ss;
        s.push(ss);
    }
    ll ans = 0;
    ll apple = 0;
    while(!s.empty()){
        string ss = s.top();
        s.pop();
        if(ss == "halfplus"){
            ++apple;
            ans += apple * m / 2;
            apple <<= 1;
        }
        else{
            ans += apple * m / 2;
            apple <<= 1;
        }
    }
    cout << ans << endl;
    return 0;
}

B

前后扫两遍    差点T.............

更好的解法是维护两个前缀和: http://www.cnblogs.com/qscqesze/p/5236749.html

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int MAXN = 5e5+5;
ll origin[MAXN] = {0};
char str[MAXN];

int main(){
    int n;
    scanf("%d", &n);
    ll ans = 0;
    ll tmp = 0;
    ll ttl = 0;
    for(int i = 0; i < n; ++i) cin >> origin[i];
    getchar();
    for(int i = 0; i < n; ++i){
        scanf("%c", &str[i]);
        if(str[i] == 'B')
            ttl += origin[i];
    }
    ans = ttl;
    tmp = ttl;
    for(int i = 0; i < n; ++i){
        if(str[i] == 'A') tmp += origin[i];
        else tmp -= origin[i];
        ans = max(ans, tmp);
    }
    tmp = ttl;
    for(int i = n-1; i >= 0; --i){
        if(str[i] == 'A') tmp += origin[i];
        else tmp -= origin[i];
        ans = max(ans, tmp);
    }
    printf("%I64d
", ans);
    return 0;
}

 C

排序输出   脑残排序函数写错了...

#include <bits/stdc++.h>
using namespace std;

vector<string> ss;

bool cmp(string a, string b){
    return a + b < b + a;
}
int main(){
    ios::sync_with_stdio(false);
    //while(true){
        ss.clear();
        int n;
        cin >> n;
        cin.get();
        for(int i = 0; i < n; ++i){
            string s;
            cin >> s;
            ss.push_back(s);
        }
        sort(ss.begin(), ss.end(), cmp);
        for(int i = 0; i < n; ++i) cout << ss[i];
        cout << endl;
    //}
    return 0;
}

D

去除大于m 的然后用类似于筛法的东西跑一边各个数因子的个数

http://www.cnblogs.com/qscqesze/p/5236807.html 

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 1e6+7;
int origin[MAXN];
int cnt[MAXN];
int dp[MAXN];

int main(){
    int n, m;
    scanf("%d %d", &n, &m);
    for(int i = 1; i <= n; ++i){
        scanf("%d", &origin[i]);
        if(origin[i] <= m) cnt[origin[i]]++;
    }
    for(int i = 1; i <= m; ++i)
        for(int j = i; j <= m; j+=i)
            dp[j] += cnt[i];
    int lcm = 1, ans = 0;
    for(int i = 1; i <= m; ++i){
        if(dp[i] > ans){
            ans = dp[i];
            lcm = i;
        }
    }
    printf("%d %d
", lcm, ans);
    for(int i = 1; i <= n; ++i)
        if(lcm % origin[i] == 0)
            printf("%d ", i);
    puts("");
    return 0;
}

E F还不敢碰