方法：dfs 染色
code:
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 #include <iostream> 5 #include <string> 6 #include <vector> 7 #include <stack> 8 #include <bitset> 9 #include <cstdlib> 10 #include <cmath> 11 #include <set> 12 #include <list> 13 #include <deque> 14 #include <map> 15 #include <queue> 16 #include <fstream> 17 #include <cassert> 18 #include <unordered_map> 19 #include <unordered_set> 20 #include <cmath> 21 #include <sstream> 22 #include <time.h> 23 #include <complex> 24 #include <iomanip> 25 #define Max(a,b) ((a)>(b)?(a):(b)) 26 #define Min(a,b) ((a)<(b)?(a):(b)) 27 #define FOR(a,b,c) for (ll (a)=(b);(a)<(c);++(a)) 28 #define FORN(a,b,c) for (ll (a)=(b);(a)<=(c);++(a)) 29 #define DFOR(a,b,c) for (ll (a)=(b);(a)>=(c);--(a)) 30 #define FORSQ(a,b,c) for (ll (a)=(b);(a)*(a)<=(c);++(a)) 31 #define FORC(a,b,c) for (char (a)=(b);(a)<=(c);++(a)) 32 #define FOREACH(a,b) for (auto &(a) : (b)) 33 #define rep(i,n) FOR(i,0,n) 34 #define repn(i,n) FORN(i,1,n) 35 #define drep(i,n) DFOR(i,n-1,0) 36 #define drepn(i,n) DFOR(i,n,1) 37 #define MAX(a,b) a = Max(a,b) 38 #define MIN(a,b) a = Min(a,b) 39 #define SQR(x) ((LL)(x) * (x)) 40 #define Reset(a,b) memset(a,b,sizeof(a)) 41 #define fi first 42 #define se second 43 #define mp make_pair 44 #define pb push_back 45 #define all(v) v.begin(),v.end() 46 #define ALLA(arr,sz) arr,arr+sz 47 #define SIZE(v) (int)v.size() 48 #define SORT(v) sort(all(v)) 49 #define REVERSE(v) reverse(ALL(v)) 50 #define SORTA(arr,sz) sort(ALLA(arr,sz)) 51 #define REVERSEA(arr,sz) reverse(ALLA(arr,sz)) 52 #define PERMUTE next_permutation 53 #define TC(t) while(t--) 54 #define forever for(;;) 55 #define PINF 1000000000000 56 #define newline ' ' 57 58 #define test if(1)if(0)cerr 59 using namespace std; 60 using namespace std; 61 typedef vector<int> vi; 62 typedef vector<vi> vvi; 63 typedef pair<int,int> ii; 64 typedef pair<double,double> dd; 65 typedef pair<char,char> cc; 66 typedef vector<ii> vii; 67 typedef long long ll; 68 typedef unsigned long long ull; 69 typedef pair<ll, ll> l4; 70 const double pi = acos(-1.0); 71 72 const int maxn = 200; 73 bool g[maxn][maxn]; 74 int color[maxn]; 75 int n, l; 76 77 bool dfs(int cur, int c) 78 { 79 if (color[cur] == -1) 80 { 81 color[cur] = c; 82 for (int i = 0; i < n; ++i) if (g[cur][i] && !dfs(i, 1-c)) return false; 83 } 84 else if (color[cur] != c) return false; 85 return true; 86 } 87 bool solve() 88 { 89 memset(color, -1, sizeof(color)); 90 for (int i = 0; i < n; ++i) if (color[i] == -1 && !dfs(i, 0)) return false; 91 return true; 92 } 93 int main() 94 { 95 while (cin >> n && n) 96 { 97 memset(g, false, sizeof(g)); 98 cin >> l; 99 for (int i = 0; i < l; ++i) 100 { 101 int u, v; cin >> u >> v; 102 g[u][v] = g[v][u] = true; 103 } 104 if (!solve()) cout << "NOT "; 105 cout << "BICOLORABLE. "; 106 } 107 } 108 109 /* 110 3 111 3 112 0 1 113 1 2 114 2 0 115 3 116 2 117 0 1 118 1 2 119 9 120 8 121 0 1 122 0 2 123 0 3 124 0 4 125 0 5 126 0 6 127 0 7 128 0 8 129 0 130 */