【HDOJ】1508 Alphacode

简单DP。考虑10、20（出现0只能唯一组合）。01（不成立）。

 1 /* 1508 */
 2 #include <iostream>
 3 #include <string>
 4 #include <map>
 5 #include <queue>
 6 #include <set>
 7 #include <stack>
 8 #include <vector>
 9 #include <deque>
10 #include <algorithm>
11 #include <cstdio>
12 #include <cmath>
13 #include <ctime>
14 #include <cstring>
15 #include <climits>
16 #include <cctype>
17 #include <cassert>
18 #include <functional>
19 #include <iterator>
20 #include <iomanip>
21 using namespace std;
22 //#pragma comment(linker,"/STACK:102400000,1024000")
23
24 #define sti                set<int>
25 #define stpii            set<pair<int, int> >
26 #define mpii            map<int,int>
27 #define vi                vector<int>
28 #define pii                pair<int,int>
29 #define vpii            vector<pair<int,int> >
30 #define rep(i, a, n)     for (int i=a;i<n;++i)
31 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
32 #define clr                clear
33 #define pb                 push_back
34 #define mp                 make_pair
35 #define fir                first
36 #define sec                second
37 #define all(x)             (x).begin(),(x).end()
38 #define SZ(x)             ((int)(x).size())
39 #define lson            l, mid, rt<<1
40 #define rson            mid+1, r, rt<<1|1
41
42 const int maxn = 1e5+5;
43 char s[maxn];
44 __int64 dp[maxn];
45
46 int main() {
47     ios::sync_with_stdio(false);
48     #ifndef ONLINE_JUDGE
49         freopen("data.in", "r", stdin);
50         freopen("data.out", "w", stdout);
51     #endif
52
53     int len;
54     __int64 ans;
55
56     while (scanf("%s", s+1)!=EOF && s[1]!=‘0‘) {
57         len = strlen(s+1);
58         rep(i, 1, len+1)    s[i] -= ‘0‘;
59
60         dp[0] = 1;
61         rep(i, 1, len+1) {
62             if (s[i] == 0) {
63                 dp[i] = dp[i-2];
64             } else if (i>1 && s[i-1]>0 && 10*s[i-1]+s[i]<=26) {
65                 dp[i] = dp[i-1] + dp[i-2];
66             } else {
67                 dp[i] = dp[i-1];
68             }
69         }
70
71         ans = dp[len];
72         printf("%I64d\n", ans);
73     }
74
75     #ifndef ONLINE_JUDGE
76         printf("time = %d.\n", (int)clock());
77     #endif
78
79     return 0;
80 }