csu1808 地铁（最短路）

一个城市中有n个站m条线路（指直接相连接u-v），也就是和城市地铁一样，在某个站换线需要花额外的时间，求1号站到n号站的最短时间消耗。
猛的一看就是普通的最短路问题，但是实际需要改变很多，不能单纯的按照原来的方式求解dis[v]表示到v的最小时间花费。
因为你无法知道这个最小值是由哪条线路过来的，会直接影响后面的换线时间消耗。所以我们纪录走i号线到v的最小时间，
这样就能明白起最小时间和哪条线路了。
dis[i],编号i的线路由u到v，那么dis[i]就表示1号站到v最后一天路径是i时的最小时间花费。

/*****************************************Author      :Crazy_AC(JamesQi)Time        :2016File Name   :*****************************************/// #pragma comment(linker, "/STACK:1024000000,1024000000")#include <iostream>#include <algorithm>#include <iomanip>#include <sstream>#include <string>#include <stack>#include <queue>#include <deque>#include <vector>#include <map>#include <set>#include <cstdio>#include <cstring>#include <cmath>#include <cstdlib>#include <climits>using namespace std;#define MEM(x,y) memset(x, y,sizeof x)#define pk push_back#define lson rt << 1#define rson rt << 1 | 1#define bug cout << "BUG HERE\n"#define debug(x) cout << #x << " = " << x << endl#define ALL(v) (v).begin(), (v).end()#define lowbit(x) ((x)&(-x))#define Unique(x) sort(ALL(x)); (x).resize(unique(ALL(x)) - (x).begin())#define BitOne(x) __builtin_popcount(x)#define showtime printf("time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)#define Rep(i, l, r) for (int i = l;i <= r;++i)#define Rrep(i, r, l) for (int i = r;i >= l;--i)typedef long long LL;typedef unsigned long long ULL;typedef pair<int,int> ii;typedef pair<ii,int> iii;const double eps = 1e-8;const double pi = 4 * atan(1);const int inf = 1 << 30;const int INF = 0x3f3f3f3f;const int MOD = 1e9 + 7;int nCase = 0;//精度正负、0的判断int dcmp(double x){if (fabs(x) < eps) return 0;return x < 0?-1:1;}template<class T> inline bool read(T &n){    T x = 0, tmp = 1;    char c = getchar();    while((c < '0' || c > '9') && c != '-' && c != EOF) c = getchar();    if(c == EOF) return false;    if(c == '-') c = getchar(), tmp = -1;    while(c >= '0' && c <= '9') x *= 10, x += (c - '0'),c = getchar();    n = x*tmp;    return true;}template <class T> inline void write(T n){    if(n < 0){putchar('-');n = -n;}    int len = 0,data[20];    while(n){data[len++] = n%10;n /= 10;}    if(!len) data[len++] = 0;    while(len--) putchar(data[len]+48);}LL QMOD(LL x, LL k) {    LL res = 1LL;    while(k) {if (k & 1) res = res * x % MOD;k >>= 1;x = x * x % MOD;}    return res;}const int maxn = 2e5 + 123;struct Edge {    int v, c, t, nxt;}e[maxn];int head[maxn], ecnt;LL dis[maxn];bool in[maxn];int n, m;inline void addedge(int u,int v,int c,int t) {    e[ecnt] = Edge {v, c, t, head[u]}, head[u] = ecnt++;    // e[ecnt] = Edge {u, c, t, head[v]}, head[v] = ecnt++;}void spfa() {    memset(dis, 0x3f, sizeof dis);    memset(in, false,sizeof in);    // cout << dis[0] << endl;    deque<int> que;    que.push_back(0);    dis[0] = 0;    while(!que.empty()) {        int idx = que.front();        que.pop_front();        int u = e[idx].v, c = e[idx].c;        in[idx] = false;        for (int i = head[u];~i;i = e[i].nxt) {            int v = e[i].v;            LL cost = (c == -1 ? 0 : abs(e[i].c - c)) + e[i].t + dis[idx];            if (dis[i] > cost) {                dis[i] = cost;                if (!in[i]) {                    in[i] = true;                    if (que.empty()) que.push_back(i);                    else if (dis[i] < dis[que.front()]) que.push_front(i);                    else que.push_back(i);                }            }        }    }}int main(int argc, const char * argv[]){        // freopen("in.txt","r",stdin);    // freopen("out.txt","w",stdout);    // ios::sync_with_stdio(false);    // cout.sync_with_stdio(false);    // cin.sync_with_stdio(false);    while(~scanf("%d%d", &n, &m)) {        memset(head, -1, sizeof head), ecnt = 0;        addedge(1, 1, -1, 0);        Rep(i, 1, m) {            int u, v, c, t;            scanf("%d%d%d%d", &u, &v, &c, &t);            addedge(u, v, c, t);            addedge(v, u, c, t);        }        spfa();        LL ans = 1e18;        // Rep(i, 0, ecnt) {        //     printf("[u = %d, dis = %lld]\n", e[i].v, dis[i]);        // }        Rep(i, 0, ecnt) if (e[i].v == n) ans = min(ans, dis[i]);        cout << ans << endl;    }    // showtime;    return 0;}