HDU5294——Tricks Device（最短路 + 最大流）

来源：互联网发布：男科网络咨询技巧编辑：程序博客网时间：2024/05/18 10:48
第一次做最大流的题目…
这题就是堆模板
#include <iostream>#include <algorithm>#include <cmath>#include <cstring>#include <cstdio>#include <cstdlib>#include <vector>#include <queue>using namespace std;typedef long long LL;const int INF = 100000000;const int MOD = 1e9 + 7;const int N = 2000 + 10;const int MAXM = 120000 + 10;int n, m;struct Node {    int from, to, next;    int cap;} edge[MAXM];int tol;int head[N];int dep[N];int gap[N]; void init() {    tol = 0;    memset(head, -1, sizeof(head));}void addedge(int u, int v, int w) {    edge[tol].from = u;    edge[tol].to = v;    edge[tol].cap = w;    edge[tol].next = head[u];    head[u] = tol++;    edge[tol].from = v;    edge[tol].to = u;    edge[tol].cap = 0;    edge[tol].next = head[v];    head[v] = tol++;}void BFS(int start, int end) {    memset(dep, -1, sizeof(dep));    memset(gap, 0, sizeof(gap));    gap[0] = 1;    int que[N];    int front, rear;    front = rear = 0;    dep[end] = 0;    que[rear++] = end;    while(front != rear) {        int u = que[front++];        if(front == N)front = 0;        for(int i = head[u]; i != -1; i = edge[i].next) {            int v = edge[i].to;            if(dep[v] != -1)continue;            que[rear++] = v;            if(rear == N)rear = 0;            dep[v] = dep[u] + 1;            ++gap[dep[v]];        }    }}int SAP(int start, int end) {    int res = 0;    BFS(start, end);    int cur[N];    int S[N];    int top = 0;    memcpy(cur, head, sizeof(head));    int u = start;    int i;    while(dep[start] < n) {        if(u == end) {            int temp = INF;            int inser;            for(i = 0; i < top; i++)                if(temp > edge[S[i]].cap) {                    temp = edge[S[i]].cap;                    inser = i;                }            for(i = 0; i < top; i++) {                edge[S[i]].cap -= temp;                edge[S[i] ^ 1].cap += temp;            }            res += temp;            top = inser;            u = edge[S[top]].from;        }        if(u != end && gap[dep[u] - 1] == 0) //出现断层，无增广路            break;        for(i = cur[u]; i != -1; i = edge[i].next)            if(edge[i].cap != 0 && dep[u] == dep[edge[i].to] + 1)                break;        if(i != -1) {            cur[u] = i;            S[top++] = i;            u = edge[i].to;        } else {            int min = n;            for(i = head[u]; i != -1; i = edge[i].next) {                if(edge[i].cap == 0)continue;                if(min > dep[edge[i].to]) {                    min = dep[edge[i].to];                    cur[u] = i;                }            }            --gap[dep[u]];            dep[u] = min + 1;            ++gap[dep[u]];            if(u != start)u = edge[S[--top]].from;        }    }    return res;}struct Edge {    int v, w;    Edge(int v, int w): v(v), w(w) {}};vector<Edge> G[N];int dis[N], cnt[N];bool vis[N];void Dijkstra(int s, int dist[]) {    priority_queue<pair<int, int> > Q;    for(int i = 0; i < n; i++)        dist[i] = INF, cnt[i] = INF;    memset(vis, 0, sizeof(vis));    Q.push(make_pair(0, s));    dist[s] = 0;    cnt[s] = 0;    while(!Q.empty()) {        int u = Q.top().second;        Q.pop();        if(vis[u]) continue ;        vis[u] = 1;        for(int i = 0; i < G[u].size(); i++) {            Edge& e = G[u][i];            if(dist[u] + e.w < dist[e.v]) {                dist[e.v] = dist[u] + e.w;                Q.push(make_pair(-dist[e.v], e.v)); // 默认大的元素优先级高，所以要取最小就加负号            }        }    }}int minEdges() {    queue<int> Q;    Q.push(0);    for(int i = 0; i < n; i++) cnt[i] = INF;    cnt[0] = 0;    while(!Q.empty()) {        int u = Q.front();        Q.pop();        if(u == n - 1) return cnt[u];        for(int i = 0; i < G[u].size(); i++) {            int v = G[u][i].v, w = G[u][i].w;            if(dis[u] + w != dis[v]) continue;            if(cnt[u] + 1 < cnt[v]) {                cnt[v] = cnt[u] + 1;                Q.push(v);            }        }    }}int main() {#ifdef Tally_Ho    freopen("in.txt", "r", stdin);#endif // Tally_Ho    while(scanf("%d%d", &n, &m) != EOF) {        int x, y, t;        for(int i = 0; i < n; i++) {            G[i].clear();        }        for(int i = 0; i < m; i++) {            scanf("%d%d%d", &x, &y, &t);            x--, y--;            G[x].push_back(Edge(y, t));            G[y].push_back(Edge(x, t));        }        Dijkstra(0, dis);        init();        for(int u = 0; u < n; u++) {            for(int i = 0; i < G[u].size(); i++) {                int v = G[u][i].v, w = G[u][i].w;                if(dis[u] + w == dis[v]) {                    addedge(u, v, 1);                }            }        }        printf("%d %d\n", SAP(0, n - 1), m - minEdges());    }    return 0;}
0 0