[BZOJ1001][BeiJing2006]狼抓兔子

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <algorithm>
#include <queue>
using namespace std;

int read() {
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
	return x * f;
}

#define maxn 1010
#define maxnode 2000010
#define maxm 6000010
#define oo 2147483647

int N, M, head[maxnode], nxt[maxm], to[maxm], dist[maxm];

void AddEdge(int a, int b, int c) {
	to[++M] = b; dist[M] = c; nxt[M] = head[a]; head[a] = M;
	swap(a, b);
	to[++M] = b; dist[M] = c; nxt[M] = head[a]; head[a] = M;
	return ;
}

int upt(int x, int y, int m) { return ((x - 1) * (m - 1) + y << 1) - 1; }
int dnt(int x, int y, int m) { return upt(x, y, m) + 1; }

struct Node {
	int u, d;
	Node() {}
	Node(int _, int __): u(_), d(__) {}
	bool operator < (const Node& t) const { return d > t.d; }
};
priority_queue <Node> Q;
int d[maxnode];
bool vis[maxnode];
void solve(int s, int t) {
	memset(vis, 0, sizeof(vis));
	for(int i = 1; i <= N; i++) d[i] = oo;
	while(!Q.empty()) Q.pop();
	d[s] = 0; Q.push(Node(s, 0));
	while(!Q.empty()) {
		int u = Q.top().u; Q.pop();
		if(vis[u]) continue;
		vis[u] = 1;
		if(u == t){ printf("%d\n", d[u]); break; }
		for(int e = head[u]; e; e = nxt[e]) if(d[to[e]] > d[u] + dist[e]) {
			d[to[e]] = d[u] + dist[e];
			if(!vis[to[e]]) Q.push(Node(to[e], d[to[e]]));
		}
	}
	return ;
}

int main() {
	int n, m; scanf("%d%d", &n, &m);
	
	if(m == 1) {
		int mn = oo;
		for(int i = 1; i < n; i++) mn = min(mn, read());
		return printf("%d\n", mn), 0;
	}
	if(n == 1) {
		int mn = oo;
		for(int i = 1; i < m; i++) mn = min(mn, read());
		return printf("%d\n", mn), 0;
	}
	
	M = 0; memset(head, 0, sizeof(head));
	N = ((n - 1) * (m - 1) << 1) + 2; int s = N - 1, t = N;
	for(int i = 1; i <= n; i++)
		for(int j = 1; j < m; j++) {
			int u, v;
			if(i == 1) {
				u = upt(i, j, m);
				AddEdge(s, u, read());
			}
			if(1 < i && i < n) {
				u = upt(i, j, m);
				v = dnt(i - 1, j, m);
				AddEdge(u, v, read());
			}
			if(i == n) {
				u = dnt(i - 1, j, m);
				AddEdge(u, t, read());
			}
		}
	for(int i = 1; i < n; i++)
		for(int j = 1; j <= m; j++) {
			int u, v;
			if(j == 1) {
				u = dnt(i, j, m);
				AddEdge(u, t, read());
			}
			if(1 < j && j < m) {
				u = upt(i, j - 1, m);
				v = dnt(i, j, m);
				AddEdge(u, v, read());
			}
			if(j == m) {
				u = upt(i, j - 1, m);
				AddEdge(s, u, read());
			}
		}
	for(int i = 1; i < n; i++)
		for(int j = 1; j < m; j++) {
			int u = upt(i, j, m), v = dnt(i, j, m);
			AddEdge(u, v, read());
		}
	
	solve(s, t);
	
	return 0;
}