【最短路】 HDOJ 3870 Catch the Theves

详细解法参考论文————两极相通——浅析最大—最小定理在信息学竞赛中的应用

论文已经讲的很详细了。。。建图跑最短路就可以了。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 200005
#define maxm 20000005
#define eps 1e-10
#define mod 1000000007
#define INF 0x3f3f3f3f
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R 
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;

struct Edge
{
	int v, c;
	Edge *next;
}pool[maxm], *H[maxn], *edges;

struct node
{
	int u, d;
	node(int u = 0, int d = 0) : u(u), d(d) {}
	bool operator < (const node& b) const {
		return d > b.d;
	}
};
priority_queue<node> q;
int dist[maxn], vis[maxn];
int g[405][405];
int n;

void addedges(int u, int v, int c)
{
	edges->v = v;
	edges->c = c;
	edges->next = H[u];
	H[u] = edges++;
}

void init(void)
{
	edges = pool;
	memset(H, 0, sizeof H);
	memset(vis, 0, sizeof vis);
	memset(dist, 0x3f, sizeof dist);
}

inline int calc(int i, int j)
{
	return (i - 1) * (n - 1) + j;
}

void read(void)
{
	scanf("%d", &n);
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			scanf("%d", &g[i][j]);
}

int dijstra(int s, int t)
{
	dist[s] = 0;
	q.push(node(s, dist[s]));
	while(!q.empty()) {
		int u = q.top().u, d = q.top().d;
		q.pop();
		if(vis[u]) continue;
		vis[u] = 1;
		for(Edge *e = H[u]; e; e = e->next) {
			if(dist[e->v] > dist[u] + e->c) {
				dist[e->v] = dist[u] + e->c;
				q.push(node(e->v, dist[e->v]));
			}
		}
	}
	return dist[t];
}

void debug(void)
{
	for(int i = 0; i <= n * n + 1; i++) {
		printf("AA %d ::\n", i);
		for(Edge *e = H[i]; e; e = e->next) {
			printf("v = %d c = %d\n", e->v, e->c);
		}
	}
}

void work(void)
{
	int s = 0, t = n * n + 1;
	for(int i = 1; i < n; i++) {
		for(int j = 1; j < n; j++) {
			if(i != n-1) {
				addedges(calc(i, j), calc(i+1, j), g[i+1][j]);
				addedges(calc(i+1, j), calc(i, j), g[i+1][j]);
			}

			if(j != n-1) {
				addedges(calc(i, j), calc(i, j+1), g[i][j+1]);
				addedges(calc(i, j+1), calc(i, j), g[i][j+1]);
			}

		}
	}
	
	for(int i = 1; i < n; i++) {
		addedges(calc(1, i), t, g[1][i]);
		addedges(t, calc(1, i), g[1][i]);
	}

	for(int i = 1; i < n; i++) {
		addedges(calc(i, n-1), t, g[i][n]);
		addedges(t, calc(i, n-1), g[i][n]);
	}

	for(int i = 1; i < n; i++) {
		addedges(calc(i, 1), s, g[i][1]);
		addedges(s, calc(i, 1), g[i][1]);
	}

	for(int i = 1; i < n; i++) {
		addedges(calc(n-1, i), s, g[n][i]);
		addedges(s, calc(n-1, i), g[n][i]);
	}
	printf("%d\n", dijstra(s, t));
}

int main(void)
{
	int _;
	while(scanf("%d", &_)!=EOF) {
		while(_--) {
			init();
			read();
			work();
		}
	}
	
	return 0;
}