71 lines
1.3 KiB
C++
71 lines
1.3 KiB
C++
#include <iostream>
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#include <cstdio>
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#include <algorithm>
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#include <cstring>
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#include <stack>
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using namespace std;
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const int N = 3e4 + 5, N3 = 15e4 + 5, inf = 0x3f3f3f3f;
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int to[N3], ne[N3], w[N3], h[N], cnt = 0, s = N - 4, e, dist[N];
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bool in[N], wa = 0;
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int u, v, w1;//WA 和bool放一起了
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int n, m, maxn = 0;
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void add(int u, int v, int w1)
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{
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to[++cnt] = v;
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ne[cnt] = h[u];
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w[cnt] = w1;
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h[u] = cnt;
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}
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void spfa(int s)
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{
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memset(dist,0x3f,sizeof dist);//更好的賦初值方法
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dist[s] = 0;//和賦inf顺序反了=白干
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stack<int> q; // queue没有自带函数清零
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q.push(s);
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while (!q.empty())
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{
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u = q.top();
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q.pop();
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in[u] = 0; // spfa的精髓！！
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for (int i = h[u]; i; i = ne[i])
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{
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v = to[i], w1 = w[i];
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// printf("%d %d %d\n",u,v,w1);
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if (dist[u] + w1 < dist[v])
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{
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dist[v] = dist[u] + w1;
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// printf("%d(%d) %d(%d) %d\n",u,dist[u],v,dist[v],w1);
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if (!in[v])
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{
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q.push(v);
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in[v] = 1;
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}
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}
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}
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}
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}
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int main()
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{
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scanf("%d%d", &n, &m);
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// for (int i = 0; i <= n; i++)
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// {
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// dist[i] = inf;
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// }
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for (int i = 1; i <= m; i++) // n,m不分
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{
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scanf("%d%d%d", &u, &v, &w1);
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add(u, v, w1);
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}
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spfa(1);
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// maxn = 0;
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// for(int i=2;i<=n;i++)
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// {
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// if(dist[i]>maxn)
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// {
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// maxn=dist[i];
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// }
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// }
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printf("%d", dist[n]);
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return 0;
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}
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