UVA1613-K-Graph Oddity（贪心）

Problem UVA1613-K-Graph Oddity

Accept: 108  Submit: 884
Time Limit: 3000 mSec

Problem Description

Input

The input will contain several test cases, each of them as described below. Consecutive test cases are separated by a single blank line.
The first line of the input file contains two integer numbers n and m, where n is the number of vertices in the graph (3 ≤ n ≤ 9999, n is odd), m is the number of edges in the graph (2 ≤ m ≤ 100000). The following m lines describe edges of the graph, each edge is described by two integers ai, bi (1 ≤ ai,bi ≤ n,ai = bi) — the vertex numbers connected by this edge. Each edge is listed at most once. The graph in the input file is connected, so there is a path between any pair of vertices.

 Output

For each test case, the output must follow the description below. The outputs of two consecutive cases will be separated by a blank line.
On the first line of the output file write a single integer number k — the minimal odd integer number, such that the degree of any vertex does not exceed k. Then write n lines with one integer number ci (1 ≤ ci ≤ k) on a line that denotes the color of i-th vertex. The colors of any two adjacent vertices must be different. If the graph has multiple different colorings, print any of them. At least one such coloring always exists.

 

 Sample Input

3 2
1 3
3 2

7 8
1 4
4 2
2 6
6 3
3 7
4 5
5 6
5 2

 

Sample Output

3
1
1
2

 

3
1
1
1
2
3
2
2

 

题解：这个题过得比较意外，一开始想从度数大的开始涂，弄一个优先队列，画了几个图，发现好像不管怎么涂都对，就写了一个然后过了，为什么是对的真的说不好，欢迎大佬指教。

 

 #include <bits/stdc++.h>

 using namespace std;

 const int maxn =  + , maxm =  + ;

 int n, m, k;

 struct Edge {
     int to, next;
 }edge[maxm << ];

 int tot, head[maxn];
 int col[maxn], deg[maxn];
 bool vis[maxn];

 void init() {
     tot = ;
     memset(head, -, sizeof(head));
     memset(deg, , sizeof(deg));
     memset(col, -, sizeof(col));
 }

 void AddEdge(int u,int v){
     edge[tot].to = v;
     edge[tot].next = head[u];
     head[u] = tot++;
 }

 void dfs(int u) {
     memset(vis, false, sizeof(vis));
     //printf("%d %d\n", fa, u);
     for (int i = head[u]; i != -; i = edge[i].next) {
         int v = edge[i].to;
         if (col[v] != -) vis[col[v]] = true;
     }

     for (int i = ; i <= k; i++) {
         if (!vis[i]) {
             col[u] = i;
             break;
         }
     }

     for (int i = head[u]; i != -; i = edge[i].next) {
         int v = edge[i].to;
         if (col[v] == -) {
             dfs(v);
         }
     }
 }

 int main()
 {
     //freopen("input.txt", "r", stdin);
     bool flag = false;
     while (~scanf("%d%d", &n, &m)) {
         if(flag) printf("\n");
         flag = true;
         init();
         int x, y;
         for (int i = ; i < m; i++) {
             scanf("%d%d", &x, &y);
             deg[x]++, deg[y]++;
             AddEdge(x, y);
             AddEdge(y, x);
         }

         int Max = ;
         for (int i = ; i <= n; i++) {
             Max = Max > deg[i] ? Max : deg[i];
         }

         k = (Max & ) ? Max : Max + ;
         dfs();
         printf("%d\n", k);
         for (int i = ; i <= n; i++) {
             printf("%d\n", col[i]);
         }
     }
     return ;
 }