[POJ3252]Round Number（数位dp）

题目链接：http://poj.org/problem?id=3252

题意：求范围内数字二进制下0的个数大于等于1的个数的数的个数。

数位dp，dp(l,zero,one,fz)记录当前第l位时0的个数1的个数和当前位是否是前导零中的部分，dfs转移就行。

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define fr first
 4 #define sc second
 5 #define cl clear
 6 #define BUG puts("here!!!")
 7 #define W(a) while(a--)
 8 #define pb(a) push_back(a)
 9 #define Rint(a) scanf("%d", &a)
10 #define Rll(a) scanf("%I64d", &a)
11 #define Rs(a) scanf("%s", a)
12 #define Cin(a) cin >> a
13 #define FRead() freopen("in", "r", stdin)
14 #define FWrite() freopen("out", "w", stdout)
15 #define Rep(i, len) for(int i = 0; i < (len); i++)
16 #define For(i, a, len) for(int i = (a); i < (len); i++)
17 #define Cls(a) memset((a), 0, sizeof(a))
18 #define Clr(a, x) memset((a), (x), sizeof(a))
19 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
20 #define lrt rt << 1
21 #define rrt rt << 1 | 1
22 #define pi 3.14159265359
23 #define RT return
24 #define lowbit(x) x & (-x)
25 #define onecnt(x) __builtin_popcount(x)
26 typedef long long LL;
27 typedef long double LD;
28 typedef unsigned long long ULL;
29 typedef pair<int, int> pii;
30 typedef pair<string, int> psi;
31 typedef pair<LL, LL> pll;
32 typedef map<string, int> msi;
33 typedef vector<int> vi;
34 typedef vector<LL> vl;
35 typedef vector<vl> vvl;
36 typedef vector<bool> vb;
37 
38 const int maxn = 34;
39 int digit[maxn];
40 LL dp[maxn][maxn][maxn][2];
41 
42 int k;
43 LL l, r;
44 
45 LL dfs(int l, int zero, int one, bool fz, bool flag) {
46   if(l == 0) return zero >= one;
47   if(!flag && ~dp[l][zero][one][fz]) return dp[l][zero][one][fz];
48   LL ret = 0;
49   int pos = flag ? digit[l] : 1;
50   Rep(i, pos+1) {
51     if(i == 0 && fz) ret += dfs(l-1, 0, one, fz, flag&&(pos==i));
52     else ret += dfs(l-1, zero+(i==0), one+(i==1), false, flag&&(pos==i));
53   }
54   if(!flag) dp[l][zero][one][fz] = ret;
55   return ret;
56 }
57 
58 LL f(LL x) {
59   int pos = 0;
60   while(x) {
61     digit[++pos] = x & 1;
62     x >>= 1;
63   }
64   return dfs(pos, 0, 0, true, true);
65 }
66 
67 signed main() {
68   //FRead();
69   Clr(dp, -1);
70   while(cin >> l >> r) {
71     cout << f(r) - f(l-1) << endl;
72   }
73   RT 0;
74 }