mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
98 lines
1.9 KiB
C++
98 lines
1.9 KiB
C++
#include <iostream>
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#include <cstdio>
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#include <cstdlib>
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#include <cmath>
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#include <algorithm>
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#include <climits>
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#include <cstring>
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#include <string>
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#include <set>
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#include <map>
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#include <queue>
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#include <stack>
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#include <vector>
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#include <list>
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#define mod 1000000007
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#define inf 0x3f3f3f3f
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#define pi acos(-1.0)
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using namespace std;
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typedef long long ll;
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#define RANGE 1005
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#define MAX 0x3f3f3f3f
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int cost[RANGE][RANGE];
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int d[RANGE];
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bool used[RANGE];
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int n,m;
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int pre[1005];
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void spfa(int s)
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{
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int i,j,now;
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for(i=0;i<=n+1;i++)
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{
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d[i]=MAX;
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used[i]=false;
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}
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int flag=0;
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for(i=0;i<=n+1;i++)
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{
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if(cost[0][i]<MAX)pre[i]=i;//初始化pre数组
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}
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used[s]=true;
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d[s]=0;
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queue<int> q;
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q.push(s);
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while(!q.empty())
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{
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now=q.front();
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q.pop();
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for(i=0;i<=n+1;i++)
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{
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if(d[i]>d[now]+cost[now][i])
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{
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d[i]=d[now]+cost[now][i];
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if(used[i]==0)
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{
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if(now!=0)pre[i]=pre[now];
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used[i]==true;
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q.push(i);
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}
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}
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if(d[i]==d[now]+cost[now][i])
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{
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if(now!=0)pre[i]=min(pre[i],pre[now]);
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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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int i,j,a,b,c;
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int we;
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scanf("%d",&we);
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while(we--)
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{scanf("%d%d",&n,&m);
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if(!n&&!m) break;
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for(i=0;i<=n+1;++i)
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{
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for(j=0;j<=i;j++)
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{
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if(i==j) cost[i][j]=0;
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else cost[i][j]=cost[j][i]=MAX;
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}
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}
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for(i=0;i<m;i++)
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{
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scanf("%d%d%d",&a,&b,&c);
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cost[a][b]=c;
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}
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spfa(0);
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if(d[n+1]<MAX)
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{
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if(pre[n+1]==n+1)printf("0\n");
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else printf("%d\n",pre[n+1]);
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}
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else printf("-1\n");
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}
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return 0;
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}
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