hdu 3986 Harry Potter and the Final Battle

次短路，枚举删掉最短路上每条边，这题是取最大值即可。

SPFA比较快。优先队列犯了个比较2的错误。。。用pair没写比较函数。

SPFA

#include <set>#include <map>#include <queue>#include <stack>#include <math.h>#include <stdio.h>#include <stdlib.h>#include <iostream>#include <limits.h>#include <string.h>#include <string>#include <algorithm>#define MID(x,y) ( ( x + y ) >> 1 )#define L(x) ( x << 1 )#define R(x) ( x << 1 | 1 )#define FOR(i,s,t) for(int i=s; i<t; i++)#define BUG puts("here!!!")using namespace std;const int MAX = 1010;const int MAX_NODE = 100010;typedef struct NODE{int to,len,id;bool flag;NODE *next;}NODE;NODE *p[MAX],node[MAX_NODE];int cou;void Add(int from,int to,int len){node[cou].next = p[from];node[cou].to = to;node[cou].len = len;node[cou].id = cou;node[cou].flag = true;p[from] = &node[cou++];}queue<int> q;int Dijkstra_List_first(int from,int to,int n){while( !q.empty() ) q.pop();int dis[MAX];int pre[MAX], id[MAX];bool used[MAX];memset(used,false,sizeof(used));for(int i=1; i<=n; i++)dis[i] = INT_MAX, pre[i] = i;dis[from] = 0;used[from] = true;int now = from;for(int i=1; i<=n; i++){NODE *head = p[now];while( head != NULL ){int len = head->len;int v = head->to;if( dis[v] > dis[now] + len ){dis[v] = dis[now] + len;pre[v] = now;id[v] = head->id;}head = head->next;}int min = INT_MAX;for(int k=1; k<=n; k++)if( !used[k] && dis[k] < min )min = dis[now = k];if( min == INT_MAX ) break;used[now] = true;}if( dis[to] == INT_MAX ) return dis[to];int f = to;while( f != from ){q.push(id[f]);f = pre[f];}return dis[to];}int SPFA_List(int from,int to,int n){queue<int> q;while( !q.empty() ) q.pop();int dis[MAX];bool inq[MAX];for(int i=1; i<=n; i++)dis[i] = INT_MAX;memset(inq,false,sizeof(inq));dis[from] = 0;q.push(from);inq[from] = 1;while( !q.empty() ){int now = q.front();q.pop();inq[now] = false;NODE *head = p[now];while( head != NULL ){int v = head->to;int len = head->len;if( dis[v] > dis[now] + len && head->flag ){dis[v] = dis[now] + len;if( !inq[v] ){inq[v] = true;q.push(v);}}head = head->next;}}return dis[to];}int solve(int n){int ans = Dijkstra_List_first(1, n, n);if( ans == INT_MAX ) return -1;ans = 0;while( !q.empty() ){int k = q.front(); q.pop();node[k].flag = false;ans = max(ans, SPFA_List(1, n, n));node[k].flag = true;}if( ans == INT_MAX ) return -1;return ans;}int main(){int ncases, n, m, u, v, len;scanf("%d", &ncases);while( ncases-- ){scanf("%d%d", &n, &m);cou = 0;memset(p, 0, sizeof(p));while( m-- ){scanf("%d%d%d", &u, &v, &len);Add(u, v, len);Add(v, u, len);}int ans = solve(n);printf("%d\n", ans);}return 0;}

优先队列

#include <set>#include <map>#include <queue>#include <stack>#include <math.h>#include <stdio.h>#include <stdlib.h>#include <iostream>#include <limits.h>#include <string.h>#include <string>#include <algorithm>#define MID(x,y) ( ( x + y ) >> 1 )#define L(x) ( x << 1 )#define R(x) ( x << 1 | 1 )#define FOR(i,s,t) for(int i=s; i<t; i++)#define BUG puts("here!!!")using namespace std;const int MAX = 1010;const int MAX_NODE = 100010;typedef struct NODE{    int to,len,id;    bool flag;    NODE *next;}NODE;NODE *p[MAX],node[MAX_NODE];int cou;void Add(int from,int to,int len){    node[cou].next = p[from];    node[cou].to = to;    node[cou].len = len;    node[cou].id = cou;    node[cou].flag = true;    p[from] = &node[cou++];}queue<int> q;int Dijkstra_List_first(int from,int to,int n){    while( !q.empty() ) q.pop();    int dis[MAX];    int pre[MAX], id[MAX];    bool used[MAX];    memset(used,false,sizeof(used));    for(int i=1; i<=n; i++)        dis[i] = INT_MAX, pre[i] = i;    dis[from] = 0;    used[from] = true;    int now = from;    for(int i=1; i<=n; i++)    {        NODE *head = p[now];        while( head != NULL )        {            int len = head->len;            int v = head->to;            if( dis[v] > dis[now] + len )            {                dis[v] = dis[now] + len;                pre[v] = now;                id[v] = head->id;            }            head = head->next;        }        int min = INT_MAX;        for(int k=1; k<=n; k++)            if( !used[k] && dis[k] < min )                min = dis[now = k];        if( min == INT_MAX ) break;        used[now] = true;    }    if( dis[to] == INT_MAX ) return dis[to];    int f = to;    while( f != from )    {        q.push(id[f]);        f = pre[f];    }    return dis[to];}typedef pair<int,int> pii;int Dijkstra_List_priority(int from,int to,int n) // 出发点，终止点，总节点 {    priority_queue<pii,vector<pii>,greater<pii> > q;    int dis[MAX];    bool used[MAX];    memset(used,false,sizeof(used));    for(int i=1; i<=n; i++)        dis[i] = INT_MAX;    dis[from] = 0;    q.push(make_pair(0, from));    while( !q.empty() )    {        int now = q.top().second; q.pop();        if( used[now] ) continue;        used[now] = true;        NODE *head = p[now];        while( head != NULL )        {            int v = head->to;            int len = head->len;            if( dis[v] > dis[now] + len && head->flag )            {                dis[v] = dis[now] + len;                q.push(make_pair(dis[v], v));            }            head = head->next;        }    }    return dis[to];}int solve(int n){    int ans = Dijkstra_List_first(1, n, n);    if( ans == INT_MAX ) return -1;    ans = 0;    while( !q.empty() )    {        int k = q.front(); q.pop();        node[k].flag = false;        ans = max(ans, Dijkstra_List_priority(1, n, n));        node[k].flag = true;    }    if( ans == INT_MAX ) return -1;    return ans;}int main(){    int ncases, n, m, u, v, len;        scanf("%d", &ncases);        while( ncases-- )    {        scanf("%d%d", &n, &m);        cou = 0;        memset(p, 0, sizeof(p));        while( m-- )        {            scanf("%d%d%d", &u, &v, &len);            Add(u, v, len);            Add(v, u, len);        }                int ans = solve(n);                printf("%d\n", ans);    }return 0;}