UVaLive 3357 Pinary (Fib数列+递归)
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题意:求第 k 个不含前导 0 和连续 1 的二进制串。
析:1,10,100,101,1000,...很容易发现长度为 i 的二进制串的个数正好就是Fib数列的第 i 个数,因为第 i 个也有子问题,其子问题也就是Fib,这样就可以用递归来解决了。
代码如下:
#pragma comment(linker, "/STACK:1024000000,1024000000") #include <cstdio> #include <string> #include <cstdlib> #include <cmath> #include <iostream> #include <cstring> #include <set> #include <queue> #include <algorithm> #include <vector> #include <map> #include <cctype> #include <cmath> #include <stack> #include <sstream> #include <list> #include <assert.h> #include <bitset> #include <numeric> #define debug() puts("++++") #define gcd(a, b) __gcd(a, b) #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 #define fi first #define se second #define pb push_back #define sqr(x) ((x)*(x)) #define ms(a,b) memset(a, b, sizeof a) #define sz size() #define be begin() #define ed end() #define pu push_up #define pd push_down #define cl clear() #define lowbit(x) -x&x //#define all 1,n,1 #define FOR(i,n,x) for(int i = (x); i < (n); ++i) #define freopenr freopen("in.in", "r", stdin) #define freopenw freopen("out.out", "w", stdout) using namespace std; typedef long long LL; typedef unsigned long long ULL; typedef pair<int, int> P; const int INF = 0x3f3f3f3f; const LL LNF = 1e17; const double inf = 1e20; const double PI = acos(-1.0); const double eps = 1e-6; const int maxn = 1000 + 10; const int maxm = 1e5 + 10; const LL mod = 1000000007; const int dr[] = {-1, 1, 0, 0, 1, 1, -1, -1}; const int dc[] = {0, 0, 1, -1, 1, -1, 1, -1}; const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"}; int n, m; const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; inline bool is_in(int r, int c) { return r >= 0 && r < n && c >= 0 && c < m; } inline int readInt(){ int x; scanf("%d", &x); return x; } vector<int> v; void dfs(int n, int last){ if(n == 0){ while(last-- > 0) putchar(‘0‘); return ; } int pos = lower_bound(v.be, v.ed, n) - v.be; if(n < v[pos]) --pos; for(int i = pos; i < last; ++i) putchar(‘0‘); putchar(‘1‘); dfs(n-v[pos], pos-1); } int main(){ v.pb(1); v.pb(1); for(int i = 2; i < 40; ++i) v.pb(v[i-1] + v[i-2]); v[0] = 0; int T; cin >> T; while(T--){ scanf("%d", &n); dfs(n, -1); putchar(‘\n‘); } return 0; }
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