poj1496

同1850

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#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

char st[15];

int com(int n, int r)
{
    if (n - r < r)
        r = n - r;
    int i, j, s = 1;
    for (i = 0, j = 1; i < r; ++i)
    {
        s *= (n - i);
        for (; j <= r && s % j == 0; ++j)
            s /= j;
    }
    return s;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%s", st) != EOF)
    {
        int len = strlen(st);
        if (len == 1)
        {
            printf("%d\n", st[0] - 'a' + 1);
            continue;
        }
        bool ok = true;
        if (st[0] <= 'z' && st[0] >= 'a')
            ok = true;
        else
            ok = false;
        for (int i = 1; i < len; i++)
            if (!(st[i] <= 'z' && st[i] >= 'a' && st[i] > st[i - 1]))
                ok = false;
        if (!ok)
        {
            printf("0\n");
            continue;
        }
        int ans = 26;
        for (int i = 2; i < len; i++)
            ans += com(26, i);
        ans += com(26, len) - com(26 - (st[0] - 'a'), len);
        for (int i = 1; i < len; i++)
            ans += com(26 - (st[i - 1] - 'a' + 1), len - i) - com(26 - (st[i]
                    - 'a'), len - i);
        printf("%d\n", ans + 1);
    }
    return 0;
}