POJ 2513 Colored Sticks（hash + 欧拉道路）

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题目链接：点击打开链接

题意：n个木棍，两端有颜色，相同颜色可以链接，问你最终能否形成一条线段。

思路：典型的欧拉道路，成立的条件是 1. 图联通。 2. 度为奇数的点不能超过2个。用map超时了，可以用hash水过去。

细节参见代码：

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<string>#include<vector>#include<stack>#include<bitset>#include<cstdlib>#include<cmath>#include<set>#include<list>#include<deque>#include<map>#include<queue>#define Max(a,b) ((a)>(b)?(a):(b))#define Min(a,b) ((a)<(b)?(a):(b))using namespace std;typedef long long ll;typedef long double ld;const ld eps = 1e-9, PI = 3.1415926535897932384626433832795;const int mod = 1000000000 + 7;const int INF = 0x3f3f3f3f;// & 0x7FFFFFFFconst int seed = 131;const ll INF64 = ll(1e18);const int maxn = 500000 + 10;const int hashsize = 1000007;int T,n,m,p[hashsize + 10],in[hashsize + 10];int res, cnt, hehe[hashsize + 10];char s[22],s2[22];int _find(int x) { return p[x] == x ? x : p[x] = _find(p[x]); }int _hash(char *s) {    int len = strlen(s), v = 1;    for(int i=0;i<len;i++) v = (v * 37 + s[i] - 'a') % hashsize;    return v;}int main() {    int cnt = 0;    for(int i=0;i<hashsize;i++) p[i] = i, hehe[i] = 0;    while(~scanf("%s%s",s,s2)) {        int a = _hash(s);        int b = _hash(s2);        if(!hehe[a]) hehe[a] = 1;        if(!hehe[b]) hehe[b] = 1;        in[a]++; in[b]++;        int x = _find(a);        int y = _find(b);        if(x != y) {            p[x] = y;        }    }    bool ok = true;    for(int i = 0; i < hashsize; i++) if(hehe[i] && _find(i) == i) ++cnt;    if(cnt > 1) ok = false;    int res = 0;    for(int i = 1; i < hashsize; i++) {        if(hehe[i]) {            if(in[i] & 1) ++res;        }    }    if(res > 2) ok = false;    if(ok) printf("Possible\n");    else printf("Impossible\n");    return 0;}

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