HDU - 2732 Leapin' Lizards(ISAP Dinic EK)
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题目大意：给出两张地图，第一张地图代表的是每根柱子的高度，第二张地图代表的是每只蜥蜴所在的位置
每根柱子只能站一只蜥蜴，蜥蜴离开该柱子时，柱子的高度会下降一个单元，当柱子的高度为0时，该柱子将不可用
现在给出每只蜥蜴能跳跃的距离，问最少有多少只蜥蜴逃不出来
解题思路：将柱子拆成2个点，权值为柱子的高度
将每只蜥蜴所在的位置和超级源点连接，权值为1
将能通到外界的柱子连接到超级汇点，权值为INF
如果柱子间的距离满足蜥蜴跳跃的距离，连接起来，权值为INF
这样图就完成了
ISAP：
#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <queue>using namespace std;#define N 2010#define INF 0x3f3f3f3fstruct Edge { int from, to, cap, flow; Edge() {} Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow) {}};struct ISAP { int p[N], num[N], cur[N], d[N]; int t, s, n, m; bool vis[N]; vector<int> G[N]; vector<Edge> edges; void init(int n, int m) { this->n = n; this->m = m; for (int i = 0; i <= n; i++) { G[i].clear(); d[i] = INF; } edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); int m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { memset(vis, 0, sizeof(vis)); queue<int> Q; d[t] = 0; vis[t] = 1; Q.push(t); while (!Q.empty()) { int u = Q.front(); Q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i] ^ 1]; if (!vis[e.from] && e.cap > e.flow) { vis[e.from] = true; d[e.from] = d[u] + 1; Q.push(e.from); } } } return vis[s]; } int Augment() { int u = t, flow = INF; while (u != s) { Edge &e = edges[p[u]]; flow = min(flow, e.cap - e.flow); u = edges[p[u]].from; } u = t; while (u != s) { edges[p[u]].flow += flow; edges[p[u] ^ 1].flow -= flow; u = edges[p[u]].from; } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; BFS(); if (d[s] > n) return 0; memset(num, 0, sizeof(num)); memset(cur, 0, sizeof(cur)); for (int i = 0; i < n; i++) if (d[i] < INF) num[d[i]]++; int u = s; while (d[s] <= n) { if (u == t) { flow += Augment(); u = s; } bool ok = false; for (int i = cur[u]; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow && d[u] == d[e.to] + 1) { ok = true; p[e.to] = G[u][i]; cur[u] = i; u = e.to; break; } } if (!ok) { int Min = n; for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (e.cap > e.flow) Min = min(Min, d[e.to]); } if (--num[d[u]] == 0) break; num[d[u] = Min + 1]++; cur[u] = 0; if (u != s) u = edges[p[u]].from; } } return flow; }};ISAP isap;#define M 110#define ABS(x) ((x) > 0 ? x : (-(x)))#include <cstring>char map1[25][M], map2[25][M];int n, d, m, cas = 1;void init() { scanf("%d%d", &n, &d); for (int i = 0; i < n; i++) scanf("%s", map1[i]); for (int i = 0; i < n; i++) scanf("%s", map2[i]); m = strlen(map1[0]); int s = n * m * 2, t = s + 1; isap.init(t, 0); for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map1[i][j] - '0') { isap.AddEdge(i * m + j, n * m + i * m + j, map1[i][j] - '0'); } int cnt = 0; for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map2[i][j] == 'L') { isap.AddEdge(s, i * m + j, 1); cnt++; } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) { if (i < d || j < d || j >= m - d || i >= n - d) { isap.AddEdge(i * m + j + n * m, t, INF); } } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) for (int k = 0; k < n; k++) for (int l = 0; l < m; l++) if (!(i == k && l == m) && d >= ABS(i - k) + ABS(j - l)) isap.AddEdge(i * m + j + n * m, k * m + l, INF); int ans = isap.Maxflow(s, t); printf("Case #%d: ", cas++); if (ans == cnt) printf("no lizard was left behind.\n"); else if(ans + 1 == cnt) printf("1 lizard was left behind.\n"); else printf("%d lizards were left behind.\n", cnt - ans);}int main() { int test; scanf("%d", &test); while (test--) { init(); } return 0;}EK
#include <cstdio>#include <cstring>#include <queue>#include <algorithm>#include <vector>using namespace std;#define N 1010#define INF 0x3f3f3f3fstruct Edge{ int from, to, cap, flow; Edge() {} Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow){}};struct EK{ vector<int> G[N]; vector<Edge> edges; int s, t, n, m, p[N]; bool vis[N]; void init(int n, int m) { this->n = n; this->m = m; for (int i = 0; i <= n; i++) G[i].clear(); edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); int m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { queue<int> q; memset(vis, 0, sizeof(vis)); vis[s] = 1; q.push(s); while (!q.empty()) { int u = q.front(); q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (!vis[e.to] && e.cap > e.flow) { vis[e.to] = true; p[e.to] = G[u][i]; if (e.to == t) return true; q.push(e.to); } } } return false; } int Augment() { int flow = INF, u = t; while (u != s) { Edge &e = edges[p[u]]; flow = min(flow, e.cap - e.flow); u = e.from; } u = t; while (u != s) { edges[p[u]].flow += flow; edges[p[u] ^ 1].flow -= flow; u = edges[p[u]].from; } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; while (BFS()) { flow += Augment(); } return flow; }};EK ek;#define M 110#define ABS(x) ((x) > 0 ? x : (-(x)))#include <cstring>char map1[25][M], map2[25][M];int n, d, m, cas = 1;void init() { scanf("%d%d", &n, &d); for (int i = 0; i < n; i++) scanf("%s", map1[i]); for (int i = 0; i < n; i++) scanf("%s", map2[i]); m = strlen(map1[0]); int s = n * m * 2, t = s + 1; ek.init(t, 0); for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map1[i][j] - '0') { ek.AddEdge(i * m + j, n * m + i * m + j, map1[i][j] - '0'); } int cnt = 0; for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map2[i][j] == 'L') { ek.AddEdge(s, i * m + j, 1); cnt++; } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) { if (i < d || j < d || j >= m - d || i >= n - d) { ek.AddEdge(i * m + j + n * m, t, INF); } } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) for (int k = 0; k < n; k++) for (int l = 0; l < m; l++) if (!(i == k && l == m) && d >= ABS(i - k) + ABS(j - l)) ek.AddEdge(i * m + j + n * m, k * m + l, INF); int ans = ek.Maxflow(s, t); printf("Case #%d: ", cas++); if (ans == cnt) printf("no lizard was left behind.\n"); else if(ans + 1 == cnt) printf("1 lizard was left behind.\n"); else printf("%d lizards were left behind.\n", cnt - ans);}int main() { int test; scanf("%d", &test); while (test--) { init(); } return 0;}Dinic
#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <queue>using namespace std;#define N 1010#define INF 0x3f3f3f3fstruct Edge{ int from, to, cap, flow; Edge() {} Edge(int from, int to, int cap, int flow) : from(from), to(to), cap(cap), flow(flow) {}};struct Dinic{ int n, m, s, t; vector<Edge> edges; vector<int> G[N]; bool vis[N]; int d[N], cur[N]; void init(int n, int m) { this->n = n; this->m = m; for (int i = 0; i <= n; i++) { G[i].clear(); } edges.clear(); } void AddEdge(int from, int to, int cap) { edges.push_back(Edge(from, to, cap, 0)); edges.push_back(Edge(to, from, 0, 0)); int m = edges.size(); G[from].push_back(m - 2); G[to].push_back(m - 1); } bool BFS() { memset(vis, 0, sizeof(vis)); queue<int> Q; Q.push(s); vis[s] = 1; d[s] = 0; while (!Q.empty()) { int u = Q.front(); Q.pop(); for (int i = 0; i < G[u].size(); i++) { Edge &e = edges[G[u][i]]; if (!vis[e.to] && e.cap > e.flow) { vis[e.to] = true; d[e.to] = d[u] + 1; Q.push(e.to); } } } return vis[t]; } int DFS(int x, int a) { if (x == t || a == 0) return a; int flow = 0, f; for (int i = cur[x]; i < G[x].size(); i++) { Edge &e = edges[G[x][i]]; if (d[x] + 1 == d[e.to] && (f = DFS(e.to, min(a, e.cap - e.flow))) > 0) { e.flow += f; edges[G[x][i] ^ 1].flow -= f; flow += f; a -= f; if (a == 0) break; } } return flow; } int Maxflow(int s, int t) { this->s = s; this->t = t; int flow = 0; while (BFS()) { memset(cur, 0, sizeof(cur)); flow += DFS(s, INF); } return flow; }};Dinic dinic;#define M 110#define ABS(x) ((x) > 0 ? x : (-(x)))#include <cstring>char map1[25][M], map2[25][M];int n, d, m, cas = 1;void init() { scanf("%d%d", &n, &d); for (int i = 0; i < n; i++) scanf("%s", map1[i]); for (int i = 0; i < n; i++) scanf("%s", map2[i]); m = strlen(map1[0]); int s = n * m * 2, t = s + 1; dinic.init(t, 0); for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map1[i][j] - '0') { dinic.AddEdge(i * m + j, n * m + i * m + j, map1[i][j] - '0'); } int cnt = 0; for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) if (map2[i][j] == 'L') { dinic.AddEdge(s, i * m + j, 1); cnt++; } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) { if (i < d || j < d || j >= m - d || i >= n - d) { dinic.AddEdge(i * m + j + n * m, t, INF); } } for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) for (int k = 0; k < n; k++) for (int l = 0; l < m; l++) if (!(i == k && l == m) && d >= ABS(i - k) + ABS(j - l)) dinic.AddEdge(i * m + j + n * m, k * m + l, INF); int ans = dinic.Maxflow(s, t); printf("Case #%d: ", cas++); if (ans == cnt) printf("no lizard was left behind.\n"); else if(ans + 1 == cnt) printf("1 lizard was left behind.\n"); else printf("%d lizards were left behind.\n", cnt - ans);}int main() { int test; scanf("%d", &test); while (test--) { init(); } return 0;} 0 0
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