POJ 2513--Colored Sticks【字典树编号 && 并查集判连通 && 欧拉路】

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Description

Input

Output

Sample Input

blue red
red violet
cyan blue
blue magenta
magenta cyan

Sample Output

Possible

无向图存在欧拉路的充要条件为：

①     图是连通的；

②     所有节点的度为偶数，或者有且只有两个度为奇数的节点。

这里用了两种方法，一种是直接分配好内存，用时：985MS

#include <cstdio>
#include <cstring>
#include <iostream>
#define maxn 500500
using namespace std;

struct node {
    int id;
    node *next[30];
};
node *root;
node tree[maxn * 10];//先分配好内存。

int du[maxn], per[maxn], color;//color 编号
int ans = 0;

node *create(){
    node *p = &tree[ans++];
    for(int i = 0 ; i < 26; ++i)
        p -> next[i] = NULL;
    return p;
};

void insert (char *s, int id){
    node *p = root;
    for(int i = 0; s[i]; ++i){
        int k = s[i] - 'a';
        if(p -> next[k] == NULL)
            p -> next[k] = create();
        p = p ->next[k];
    }
    p -> id = id;
}

int search (char *s){
    node *p = root;
    for(int i = 0; s[i]; ++i){
        int k = s[i] - 'a';
        if(p -> next[k] == NULL)
            return 0;
        p = p -> next[k];
    }
    return p->id;
}

void init(){
    for(int i = 1; i <= maxn; ++i)
        per[i] = i;
    memset(du, 0 ,sizeof(du));
    color = 0;
}

int find(int x){
    int r = x;
    while( r != per[r])
        r = per[r];
    per[x] = r;
    return r;
}

void join (int x, int y){
    int fx = find(x);
    int fy = find(y);
    per[fx] = fy;
}

bool judge(){
	int sum = 0; 
    for(int  i = 1; i <= color; ++i)
        if(du[i] % 2 == 1)  sum++;
    if(sum != 0 && sum != 2)    return false;
    int k = find(1);
    for(int  i = 2; i <= color; ++i)
        if(k != find(i))
            return false;
    return true;
}

int main (){
    char s1[15], s2[15];
    init();
    root = create();
    while(cin >> s1 >> s2){
        int x = search(s1);
        int y = search(s2);
        if(!x) insert(s1,x = ++color);
        if(!y) insert(s2,y = ++color);
        du[x]++, du[y]++;
        join(x, y);
    }
    if(judge())
        printf("Possible\n");
    else
        printf("Impossible\n");

    return 0;
}

#include <cstdio>
#include <cstring>
#include <iostream>
#define maxn 500500
using namespace std;

struct node {
    int id;//纪录颜色的编号 
    node *next[30];
};
node *root;
//node tree[maxn * 10];//先分配好内存。

int du[maxn], per[maxn], color;

//int ans = 0;
//node *create(){
//    node *p = &tree[ans++];
//    for(int i = 0 ; i < 26; ++i)
//        p -> next[i] = NULL;
//    return p;
//};

void insert (char *s, int id){
    node *p = root;
    for(int i = 0; s[i]; ++i){
        int k = s[i] - 'a';
        if(p -> next[k] == NULL){
        	node *q = new node;
        	memset(q -> next,NULL,sizeof(q -> next));
        	p -> next[k]= q;
		} 
        p = p ->next[k];
    }
    p -> id = id;
}

int search (char *s){
    node *p = root;
    for(int i = 0; s[i]; ++i){
        int k = s[i] - 'a';
        if(p -> next[k] == NULL)
            return 0;
        p = p -> next[k];
    }
    return p->id;
}

void init(){
    for(int i = 1; i <= maxn; ++i)
        per[i] = i;
    memset(du, 0 ,sizeof(du));
    color = 0;
}

void initroot(){
	root = new node;
	memset(root -> next, NULL, sizeof(root->next)); 
} 
int find(int x){
    int r = x;
    while( r != per[r])
        r = per[r];
    per[x] = r;
    return r;
}

void join (int x, int y){
    int fx = find(x);
    int fy = find(y);
    per[fx] = fy;
}

bool judge(){
	int sum = 0; 
    for(int  i = 1; i <= color; ++i)
        if(du[i] % 2 == 1)  sum++;
    if(sum != 0 && sum != 2)    return false;
    int k = find(1);
    for(int  i = 2; i <= color; ++i)
        if(k != find(i))
            return false;
    return true;
}

int main (){
    char s1[15], s2[15];
    init();
    initroot();
    //root = create();
    while(cin >> s1 >> s2){
        int x = search(s1);
        int y = search(s2);
        if(!x) insert(s1,x = ++color);
        if(!y) insert(s2,y = ++color);
        du[x]++, du[y]++;
        join(x, y);
    }
    if(judge())
        printf("Possible\n");
    else
        printf("Impossible\n");

    return 0;
}

POJ 2513--Colored Sticks【字典树编号 && 并查集判连通 && 欧拉路】

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原文地址：http://blog.csdn.net/hpuhjh/article/details/47156573