BZOJ 2763: [JLOI2011]飞行路线 最短路

题目链接:

http://www.lydsy.com/JudgeOnline/problem.php?id=2763

题意:

题解:

最短路，在转移dis的时候多开一维k就好了
dis[i][j]->dis[t][j]+e[i][t]
dis[i][j]->dis[t][j+1] if j

代码:

#include <bits/stdc++.h>using namespace std;typedef long long ll;#define MS(a) memset(a,0,sizeof(a))#define MP make_pair#define PB push_backconst int INF = 0x3f3f3f3f;const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;inline ll read(){    ll x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}//////////////////////////////////////////////////////////////////////////const int maxn = 1e5+10;struct node{    int x,y;};vector<node> E[maxn];ll dis[maxn][15];int inq[maxn][15];int main(){    int n,m,k,s,t;    scanf("%d%d%d%d%d",&n,&m,&k,&s,&t);    for(int i=0; i<m; i++){        int u,v,w; scanf("%d%d%d",&u,&v,&w);        E[u].push_back(node{v,w});        E[v].push_back(node{u,w});    }    for(int i=0; i<=n; i++)        for(int j=0; j<=k; j++)            dis[i][j] = INF;    memset(inq,0,sizeof(inq));    queue<node> q;    q.push((node){s,0});    inq[s][0] = 1, dis[s][0] = 0;    while(!q.empty()){        node now = q.front();        q.pop(); inq[now.x][now.y] = 0;        for(int i=0; i<(int)E[now.x].size(); i++){            int v = E[now.x][i].x, w = E[now.x][i].y;            if(dis[v][now.y] > dis[now.x][now.y]+w){ // 不用票                dis[v][now.y] = dis[now.x][now.y]+w;                if(!inq[v][now.y]){                    inq[v][now.y] = 1;                    q.push((node){v,now.y});                }            }            if(dis[v][now.y+1]>dis[now.x][now.y] && now.y<k){ // 用票                dis[v][now.y+1] = dis[now.x][now.y];                if(!inq[v][now.y+1]){                    inq[v][now.y+1] = 1;                    q.push((node){v,now.y+1});                }            }        }    }    ll ans = INF;    for(int i=0; i<=k; i++)        if(dis[t][i] < ans)            ans = dis[t][i];    cout << ans << endl;    return 0;}