Codeforces Round #299 (Div. 2)

A题,水题,注意单词别打错了

/*************************************************************************
    > File Name: CF-299-A.cpp
    > Author: ALex
    > Mail: zchao1995@gmail.com 
    > Created Time: 2015年04月15日 星期三 15时30分49秒
 ************************************************************************/

#include <functional>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <map>
#include <bitset>
#include <set>
#include <vector>

using namespace std;

const double pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const double eps = 1e-15;
typedef long long LL;
typedef pair <int, int> PLL;

string str[100];

int main()
{
    str[0] = "zero";
    str[1] = "one";
    str[2] = "two";
    str[3] = "three";
    str[4] = "four";
    str[5] = "five";
    str[6] = "six";
    str[7] = "seven";
    str[8] = "eight";
    str[9] = "nine";
    str[10] = "ten";
    str[11] = "eleven";
    str[12] = "twelve";
    str[13] = "thirteen";
    str[14] = "fourteen";
    str[15] = "fifteen";
    str[16] = "sixteen";
    str[17] = "seventeen";
    str[18] = "eighteen";
    str[19] = "nineteen";
    str[20] = "twenty";
    str[30] = "thirty";
    str[40] = "forty";
    str[50] = "fifty";
    str[60] = "sixty";
    str[70] = "seventy";
    str[80] = "eighty";
    str[90] = "ninety";
    int s;
    while (~scanf("%d", &s))
    {
        if (s < 10)
        {
            cout << str[s] << endl;
        }
        else if (s < 20)
        {
            cout << str[s] << endl;
        }
        else if (s % 10 == 0)
        {
            cout << str[s] << endl;
        }
        else
        {
            int a = s - s % 10;
            int b = s % 10;
            cout << str[a] << "-" << str[b] << endl;
        }
    }
    return 0;
}

B,这样的数不多,dfs一遍处理出来,排个序然后就找好了

/*************************************************************************
    > File Name: CF-299-B.cpp
    > Author: ALex
    > Mail: zchao1995@gmail.com 
    > Created Time: 2015年04月15日 星期三 15时44分07秒
 ************************************************************************/

#include <functional>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <map>
#include <bitset>
#include <set>
#include <vector>

using namespace std;

const double pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const double eps = 1e-15;
typedef long long LL;
typedef pair <int, int> PLL;

vector <LL> num;

int pos;

void dfs(int cur, LL sum)
{
    num.push_back(sum);
    if (cur > 9)
    {
        return;
    }
    dfs(cur + 1, sum * 10 + 4);
    dfs(cur + 1, sum * 10 + 7);
}

int main()
{
    LL n;
    num.clear();
    dfs(1, 0);
    sort(num.begin(), num.end());
    while (cin >> n)
    {
        int pos = lower_bound(num.begin(), num.end(), n) - num.begin();
        cout << pos << endl;
    }
}

C: 二分直接搞

/*************************************************************************
    > File Name: CF-299-C.cpp
    > Author: ALex
    > Mail: zchao1995@gmail.com 
    > Created Time: 2015年04月15日 星期三 16时35分46秒
 ************************************************************************/

#include <functional>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <map>
#include <bitset>
#include <set>
#include <vector>

using namespace std;

const double pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const double eps = 1e-15;
typedef long long LL;
typedef pair <int, int> PLL;

int main()
{
    int A, B, n;
    while (~scanf("%d%d%d", &A, &B, &n))
    {
        while (n--)
        {
            LL l, t, m;
            cin >> l >> t >> m;
            LL high = A + (l - 1) * B;
            if (high > t)
            {
                printf("-1\n");
                continue;
            }
            double x = (t - A) * 1.0 / B + 1;
            LL left = l, right = (LL)x;
            LL mid;
            LL ans = -1;
            while (left <= right)
            {
                mid = (left + right) >> 1;
                LL h = A + (mid - 1) * B;
                LL sum = (2 * A + (mid - 1) * B) * mid / 2;
                sum -= (2 * A + (l - 2) * B) * (l - 1) / 2;
                LL cnt = sum / m + ((sum % m) ? 1 : 0);
                if (cnt <= t)
                {
                    left = mid + 1;
                    ans = mid;
                }
                else
                {
                    right = mid - 1;
                }
            }
            cout << ans << endl;
        }
    }
    return 0;
}

D,方法很多,我用Ekmp来处理的,方便判断某个前缀是否是自身的后缀,然后for一遍计数

/*************************************************************************
    > File Name: CF-299-D.cpp
    > Author: ALex
    > Mail: zchao1995@gmail.com 
    > Created Time: 2015年04月15日 星期三 16时05分56秒
 ************************************************************************/

#include <functional>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <map>
#include <bitset>
#include <set>
#include <vector>

using namespace std;

const double pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const double eps = 1e-15;
typedef long long LL;
typedef pair <int, int> PLL;

static const int N = 1000100;
static const int mod = 1000000007;

int nxt[N];
char str[N];
LL base2[N];
int pos[N];

void EXTEND_KMP()
{
    int lens = strlen(str);
    nxt[0] = lens;
    int i, j, p, L;
    j = 0;
    while (j + 1 < lens && str[j] == str[j + 1])
    {
        ++j;
    }
    nxt[1] = j;
    int a = 1;
    for (i = 2; i < lens; ++i)
    {
        p = nxt[a] + a - 1;
        L = nxt[i - a];
        if (i + L < p + 1)
        {
            nxt[i] = L;
        }
        else
        {
            j = max(0, p - i + 1);
            while (i + j < lens && str[i + j] == str[j])
            {
                ++j;
            }
            nxt[i] = j;
            a = i;
        }
    }
}

int main()
{
    base2[0] = 1;
    for (int i = 1; i <= 1000000; ++i)
    {
        base2[i] = base2[i - 1] * 26 % mod;
    }
    int n, m;
    while (~scanf("%d%d", &n, &m))
    {
        scanf("%s", str);
        int len = strlen(str);
        EXTEND_KMP();
        for (int i = 1; i <= m; ++i)
        {
            scanf("%d", &pos[i]);
            --pos[i];
        }
        if (m == 0)
        {
            cout << base2[n] << endl;
            continue;
        }
        LL ans = 1;
        bool flag = 1;
        if (pos[1] > 0)
        {
            ans *= base2[pos[1]];
        }
        if (pos[1] + len > n)
        {
            printf("0\n");
            continue;
        }
        int last = pos[1] + len - 1; // last position
        for (int i = 2; i <= m; ++i)
        {
            if (pos[i] + len > n)
            {
                flag = 0;
                break;
            }
            if (pos[i] > last)
            {
                ans *= base2[pos[i] - 1 - last];
                ans %= mod;
                last = pos[i] + len - 1;
            }
            else
            {
                int repos = last - pos[i] + 1;
                repos = len - repos;
                if (nxt[repos] != last - pos[i] + 1)
                {
                    flag = 0;
                    break;
                }
                last = pos[i] + len - 1;
            }
        }
        if (!flag)
        {
            printf("0\n");
            continue;
        }
        if (last < n - 1)
        {
            ans *= base2[n - 1 - last];
            ans %= mod;
        }
        cout << ans << endl;
    }
    return 0;
}