【图论】[luoguP2731]骑马修栅栏 Riding the Fences

题目

半年前刚学图论的时候就做过 今天竟然忘了 翻书才想起来欧拉路。。
也就是一笔画问题 深搜就可以了

代码如下

#include<iostream>#include<cstdio>#include<cctype>    using namespace std;    #define in = read();    typedef long long ll;    typedef unsigned int ui;    const ll size = 1500 + 10;        int f , x , y;        int map[size][size];        int start = 1 , minn , maxx , len;        int ans[size] , du[size];inline ll read(){        ll num = 0 , f = 1;    char ch = getchar();        while(!isdigit(ch)){                if(ch == '-')   f = -1;                ch = getchar();        }        while(isdigit(ch)){                num = num*10 + ch - '0';                ch = getchar();        }        return num*f;}void dfs(int i){        for(register int j=minn;j<=maxx;j++)                if(map[i][j]){                        map[i][j] --;                        map[j][i] --;                        dfs(j);                }        ans[++ len] = i;}int main(){        f in;        for(register int i=1;i<=f;i++){                x in;   y in;                map[x][y] ++;   map[y][x] ++;                du[x] ++;   du[y] ++;                minn = min(min(x , minn) , y);                maxx = max(max(x , maxx) , y);        }        for(register int i=minn;i<=maxx;i++)                if(du[i]%2 == 1){                        start = i;                        break;                }        dfs(start);        for(register int i=len;i>=1;i--)                printf("%d\n" , ans[i]);}//COYG