bzoj3033: 太鼓达人 欧拉路径

题目链接

bzoj3033: 太鼓达人

题解

对于k-1位点，k位二进制位边，将点的转移连起来

每个点的入度和出度相等并且全部是偶点

只需要在这个图中找字典序最小的欧拉回路

可以贪心地找字典序较小的边，然后实在不行了就回溯

代码

#include<cstdio>
#include<cstring>
#include<algorithm>
#define rep(p,x,k) for(int p = x;p <= k;++ p)
#define per(p,x,k) for(int p = x;p >= k;-- p)
#define gc getchar()
#define pc putchar
#define LL long long
inline LL read() {
    LL x = 0,f = 1;
    char c = gc;
    while(c < '0' || c > '9') c = gc;
    while(c <= '9' && c >= '0') x = x * 10 + c -'0',c = gc;
    return x ;
}
void print(LL x) {
    if(x < 0) {
        pc('-');
        x = -x;
    }
    if(x >= 10) print(x / 10);
    pc(x % 10 + '0');
}
int m,l;
bool vis[100007];
int ans[100007];
bool dfs(int s,int k) {
    if(vis[s]) return 0;
    if(k == l) return 1;
    vis[s] = 1;
    ans[k] = s & 1;
    if (dfs((s << 1) & (l - 1), k + 1) )return 1;
    if (dfs((s << 1 | 1) & (l - 1),k + 1)) return 1;
    vis[s] = 0;
    return 0;
}
int main() {
    m = read();
    print(l = 1 << m);
    pc(' ');
    dfs(0,1);
    for(int i = 1;i < m;++ i) pc('0');
    for(int i = 1;i <= l - m + 1;++ i) pc(ans[i] + '0');
    return 0;
}