Uva 10596 Morning Walk

 

Problem H	Morning Walk
Time Limit	3 Seconds

题目链接：

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=1537

Problemsetter: Muhammad Abul Hasan

International Islamic University Chittagong

 解题思路：

感觉跟上一题一样，都是欧拉回路，这次不用打印较为简单，感觉欧拉回路开始有个模板了，判断结点度数的奇偶，DFS或者BFS或者并查集判断连通。

刚开始理解错题目了，以为可以是欧拉回路或通路，而且看他的输入以为是有向图，差的太远了，故WA了几次~~但改了之后还是WA了很多次，逃了一节课找了很久还是没找出来，最后干脆重新写过 AC了，感觉弱爆了！

#include<stdio.h>
#include<string.h>
#define MAXN 220
int road[MAXN][MAXN];
int visit[MAXN];
int note[MAXN];
int sum;

int DFS(int current, int n)
{
    int j;
    sum++;
    visit[current] = 1;
    for(j=0; j<n; ++j)
    {
        if(road[current][j]  && !visit[j])
        DFS(j, n);
    }
    return 1;
}

int main()
{
    int i, j, n, r, flag, x, y;
    while(scanf("%d%d", &n, &r) != EOF)
    {
        memset(road, 0, sizeof(road));
        memset(note, 0, sizeof(note));
        for(i=0; i<r; ++i)
        {
            scanf("%d%d", &x, &y);
            road[x][y]++;
            road[y][x]++;
            note[x]++, note[y]++;
        }
        flag = 0;
        for(i=0; i<n; ++i)
        {
            if(note[i]%2)
            {
                flag = 1;
                break;
            }
        }
        if(flag)
        {
            printf("Not Possible\n");
        }
        else
        {
            memset(visit, 0, sizeof(visit));
            sum = 0;
            DFS(0, n);
            if(sum != n)
            printf("Not Possible\n");
            else printf("Possible\n");
        }    
    }
    return 0;
}

#include<stdio.h>
#include<string.h>
#define MAXN 202
int road[MAXN][MAXN];
int note[MAXN][2];
int visit[MAXN];

int Dfs(int current, int n)
{
    int j;
    visit[current] = 1;
    for(j=0; j<n; ++j)
    if(note[current][j] != 0 && !visit[j])
    Dfs(j, n);
}
int main()
{
    freopen("input.txt", "r", stdin);
    int n, r, i, j, x, y, flag, cnt, temp,store;
    while(scanf("%d%d", &n, &r) != EOF)
    {
        memset(road, 0, sizeof(road));
        memset(note, 0, sizeof(note));
        for(i=0; i<r; ++i)
        {
            scanf("%d%d", &x, &y);
            road[x][y]++;
            note[x][0]++, note[y][1]++;
        }
        cnt = flag = store = 0;
        for(i=0; i<n; ++i)
        if(note[i][0] != 0)
        {
            memset(visit, 0, sizeof(visit));
            Dfs(i, n);
             for(j=0; j<n; ++j)
             if(!visit[j] && (note[j][0] != 0 || note[j][1] != 0))
             flag = 1;
            break;
        }
        for(i=0; i<n && flag == 0; ++i)
        {
            if(note[i][0] != 0 || note[i][1] != 0)
            {
                temp = note[i][0] - note[i][1];
                if(temp == -1 || temp == 1)
                {
                    cnt++;
                    store += temp;
                }
                else if(temp != 0) 
                {
                    flag = 1;
                    break;
                }
            }
            if(flag == 1) break;
        }
        if(flag == 1 || cnt > 2 || store != 0)
        {
            printf("Not Possible\n");
        }
        else printf("Possible\n");
    }
    return 0;
}