大意:Dandelion's uncle的工厂开始分红,厂里的工人们有些有特殊的要求,如A工人的工资一定要大于B,B工人的工资一定要大于C,而不能出现A > B,B> C,C > A的情况。
思路:拓扑排序。(基于邻接表BFS拓扑排序,邻接矩阵会MLE)。
CODE:
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <queue>
using namespace std;
const int M = 10005;
int u[4*M], v[4*M], next[4*M], w[4*M], topo[4*M];
int first[M], d[M];
int ind[M], money[M];
int n, m, cnt, tot;
void init()
{
cnt = tot = 0;
memset(ind, 0, sizeof(ind));
memset(first, -1, sizeof(first));
memset(topo, 0, sizeof(topo));
for(int i = 1; i <= n; i++) money[i] = 888;
}
void read_graph(int u1, int v1)
{
v[cnt] = v1; next[cnt] = first[u1]; first[u1] = cnt++;
}
int toposort()
{
queue<int> q;
int ans = 0;
for(int i = 1; i <= n; i++) if(!ind[i])
q.push(i);
while(!q.empty())
{
int x = q.front(); q.pop();
topo[++tot] = x;
ans += money[x];
for(int e = first[x]; e!=-1; e = next[e])
{
if(--ind[v[e]] == 0)
{
money[v[e]] = money[x]+1;
q.push(v[e]);
}
}
}
if(tot != n) return -1;
return ans;
}
int main()
{
while(~scanf("%d%d", &n, &m))
{
init();
while(m--)
{
int u1, v1;
scanf("%d%d", &u1, &v1);
read_graph(v1, u1); //反向处理边,从而好求最小金钱。
ind[u1]++;
}
int ans = toposort();
if(ans != -1)
{
printf("%d\n", ans);
}
else printf("-1\n");
}
return 0;
}
#include <cstdio>
#include <cstdlib>
#include <queue>
using namespace std;
const int M = 10005;
int u[4*M], v[4*M], next[4*M], w[4*M], topo[4*M];
int first[M], d[M];
int ind[M], money[M];
int n, m, cnt, tot;
void init()
{
cnt = tot = 0;
memset(ind, 0, sizeof(ind));
memset(first, -1, sizeof(first));
memset(topo, 0, sizeof(topo));
for(int i = 1; i <= n; i++) money[i] = 888;
}
void read_graph(int u1, int v1)
{
v[cnt] = v1; next[cnt] = first[u1]; first[u1] = cnt++;
}
int toposort()
{
queue<int> q;
int ans = 0;
for(int i = 1; i <= n; i++) if(!ind[i])
q.push(i);
while(!q.empty())
{
int x = q.front(); q.pop();
topo[++tot] = x;
ans += money[x];
for(int e = first[x]; e!=-1; e = next[e])
{
if(--ind[v[e]] == 0)
{
money[v[e]] = money[x]+1;
q.push(v[e]);
}
}
}
if(tot != n) return -1;
return ans;
}
int main()
{
while(~scanf("%d%d", &n, &m))
{
init();
while(m--)
{
int u1, v1;
scanf("%d%d", &u1, &v1);
read_graph(v1, u1); //反向处理边,从而好求最小金钱。
ind[u1]++;
}
int ans = toposort();
if(ans != -1)
{
printf("%d\n", ans);
}
else printf("-1\n");
}
return 0;
}