强联通分量容易出错的地方

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这个题强联通分量容易出错的地方我都出了我把它记下来。。。

#include <iostream>

#include <cstdio>

#include <cstring>

#define clr(x) memset(x, 0, sizeof(x))

using namespace std;

const int maxn = 50005;

const int maxm = 50005;

struct Edge {

int to, next;

}e[maxm];

int head[maxn], tot;

void add(int u, int v) {

e[tot].to = v;

e[tot].next = head[u];

head[u] = tot++;

}

int min(int a, int b) {

return a > b ? b : a;

}

int n, m;

int dfn[maxn], low[maxn], id[maxn], outd[maxn], s[maxn], ins[maxn];

int s_cnt, ans_cnt, cnt;

void init() {

clr(head);

clr(dfn); clr(low); clr(id);clr(outd); clr(ins);

tot = 1;

s_cnt = 0;

ans_cnt = 0;

cnt = 1;

}

void dfs(int u) {

s[s_cnt++] = u;

ins[u] = 1;

for(int i = head[u]; i; i = e[i].next) {

int v = e[i].to;

if(!dfn[v]) {

dfn[v] = low[v] = cnt++;

dfs(v);

low[u] = min(low[u], low[v]);

} else if(ins[v]){

low[u] = min(low[u], dfn[v]);

}

if(dfn[u] == low[u]) {

ans_cnt++;

int x;

do {

x = s[--s_cnt];

ins[x] = 0;

id[x] = ans_cnt;

} while(x != u);

}

int main() {

int x, y;

while(EOF != scanf("%d %d",&n, &m) ) {

init();

for(int i = 1; i <= m; i++) {

scanf("%d %d",&x, &y);

add(x, y);

}

for(int i = 1; i <= n; i++) {

if(!dfn[i]) {

dfn[i] = low[i] = cnt++;

dfs(i);

}

if(ans_cnt == 1) {

printf("%d\n", n);

continue;

}

for(int i = 1; i <= n; i++) {

for(int j = head[i]; j; j = e[j].next) {

int k = e[j].to;

if(id[i] != id[k])

outd[id[i]]++;

}

int flag = 0;

for(int i = 1; i <= ans_cnt; i++) {

if(outd[i] == 0) {

if(flag == 0) flag = i;

else {

flag = 0;

break;

}

if(flag == 0) {

puts("0");

} else {

int sum = 0;

for(int i = 1; i <= n; i++) {

if(id[i] == flag) {

sum++;

}

printf("%d\n", sum);

}

return 0;

}

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