洛谷P1137 旅行计划

题目链接：

kma

题目分析：

其实不需要dp的，直接拓扑排序就可以了

代码：

#include <bits/stdc++.h>
#define N (500000 + 50)
using namespace std;
inline int read() {
	int cnt = 0, f = 1; char c = getchar();
	while (!isdigit(c)) {if (c == '-') f = -f; c = getchar();}
	while (isdigit(c)) {cnt = (cnt << 3) + (cnt << 1) + c - '0'; c = getchar();}
	return cnt * f;
}
int nxt[N], to[N], first[N], tot, p;
int topo[N];
int in[N], a[N];
queue <int> q;
int n, m, u, v;
void Add(int x, int y) {
	nxt[++tot] = first[x];
	first[x] = tot;
	to[tot] = y;
}
void bfs() {
	for (int i = 1; i <= n; i++) {
		if (!in[i]) q.push(i), topo[i] = 1;
	}
	while (!q.empty()) {
		int v = q.front(); q.pop();
		for (register int i = first[v]; i; i = nxt[i]) {
			int vv = to[i];--in[vv];
			if (!in[vv]) q.push(vv), topo[vv] = max(topo[vv], topo[v] + 1);
		}
	}
}

int main() {
	n = read(), m = read();
	for (register int i = 1; i <= m; i++) {
		u = read(), v = read();
		++in[v];
		Add(u, v);
	}
	bfs();
	for (register int i = 1; i <= n; i++) printf("%d
", topo[i]);
	return 0;
}