版权声明:_ https://blog.csdn.net/lunch__/article/details/81808222
这题好玄学啊… 它真的让我对 这个算法绝望了 完全学不懂
首先这个题要我们求每条边所属的集合
当然还是不考虑存边 存完点 一遍就好了啦
Codes
#include<bits/stdc++.h>
int read() {
int _ = 0, ___ = 1; char __ = getchar();
for(; !isdigit(__); __ = getchar()) if(__ == '-') ___ = -1;
for(; isdigit(__); __ = getchar()) _ = (_ << 3) + (_ << 1) + (__ ^ 48);
return _ * ___;
}
using namespace std;
const int N = 2e4 + 10, M = 4e5 + 10;
int head[N], nxt[M], to[M], e = 1;
int n, m, ins[N], Sta[M], top, cnt, ans[M];
int dfn[N], low[N], color, be[M], num[M];
vector<int> kuai[N];
void add(int x, int y) {
to[++ e] = y; nxt[e] = head[x]; head[x] = e;
}
void dfs(int x, int fa) {
int sz = 0;
//cerr << x << endl;
//cout << x << ' ' << fa << endl;
dfn[x] = low[x] = ++ cnt; Sta[++ top] = x;
for(int i = head[x]; i; i = nxt[i]) {
if(!dfn[to[i]]) {
++ sz;
dfs(to[i], x);
low[x] = min(low[x], low[to[i]]);
if(low[to[i]] >= dfn[x]) {
++ color;
do {
be[Sta[top]] = color;
kuai[color].push_back(Sta[top]);
}while(Sta[top --] != to[i]);
kuai[color].push_back(x);
}
}
else if(to[i] != fa && !ins[to[i]])
low[x] = min(low[x], dfn[to[i]]);
}
}
void Dfs(int x) {
//cerr << x << endl;
for(int i = head[x]; i; i = nxt[i])
if(!ans[i >> 1] && be[to[i]] == be[x]) {
// 这里我原来是用一个数组判定 但是不知道为什么一直Wa
// 抱着试一下的心情调成这样才过了这个题
// ins[i] = ins[i ^ 1] = 1;
ans[i >> 1] = be[x];
num[be[x]] = min(num[be[x]], i >> 1);
Dfs(to[i]);
//ins[i] = ins[i ^ 1] = 0;
}
}
int main() {
freopen("1190.in", "r", stdin);
freopen("1190.out", "w", stdout);
int x, y;
n = read(), m = read();
for(int i = 1; i <= m; ++ i) {
x = read(), y = read();
add(x, y); add(y, x);
num[i] = INT_MAX;
}
dfs(1, 0);
for(int i = 1; i <= color; ++ i) {
for(int j = 0, sz = kuai[i].size(); j < sz; ++ j)
be[kuai[i][j]] = i;
Dfs(kuai[i][0]);
}
cout << color << endl;
for(int i = 1; i <= m; ++ i)
printf("%d ", num[ans[i]]);
puts("");
return 0;
}