HDU-3035-War

ACM模版

描述

题解

这是我做过建图最复杂的题，单看问题，感觉是最小割（最大流），但是点数数百万，根本搞不定啊，所以可以转化成最短路来做，提供一个比较好的相关知识的PPT——浅析最大最小定理在信息学竞赛中的应用……我也刚接触这个，明天进一步学习，要睡了，医生说，以后不能再熬夜了，不然……~/(ㄒoㄒ)/

代码

#include <cstdio>
#include <queue>
#include <cstring>
#include <iostream>

using namespace std;

const int MAXN = 1000100;
const int MAXM = 7000000;
const int INF = 0x3f3f3f3f;

struct node
{
int v, d;
node(int _v, int _d) : v(_v), d(_d) {}
bool operator < (const node a) const
{
return a.d < d;
}
};

int n, m, en, S, T;
int head[MAXN];

struct Edge
{
int v, w, next;
Edge() {}
Edge(int _v, int _w, int _next) : v(_v), w(_w), next(_next) {}
} e[MAXM];

inline void add(int u, int v, int w)
{
e[en].v = v;
e[en].w = w;
e[en].next = head[u];
head[u] = en++;
e[en].v = u;
e[en].w = w;
e[en].next = head[v];
head[v] = en++;
}

void initGraph()
{
en = S = 0;
T = n * m * 4 + 1;
for (int i = S; i <= T; i++)
{
head[i] = -1;
}

int x, y, z;
for (int j = 0; j < m; j++)
{
x = j * 4 + 1;
scanf("%d", &z);
add(S, x, z);
}
for (int i = 1; i < n; i++)
{
for (int j = 0; j < m; j++)
{
y = (i * m + j) * 4 + 1;
x = y - m * 4 + 3;
scanf("%d", &z);
add(x, y, z);
}
}
for (int j = 0; j < m; j++)
{
x = ((n - 1) * m + j) * 4 + 4;
scanf("%d", &z);
add(x, T, z);
}
for (int i = 0; i < n; i++)
{
scanf("%d", &z);
add(i * m * 4 + 2, T, z);
for (int j = 1; j < m; j++)
{
y = (i * m + j) * 4 + 2;
x = y - 3;
scanf("%d", &z);
add(x, y, z);
}
scanf("%d", &z);
add(S, (i + 1) * m * 4 - 1, z);
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
x = (i * m + j) * 4 + 1;
scanf("%d", &z);
add(x, x + 1, z);
scanf("%d", &z);
add(x, x + 2, z);
}
for (int j = 0; j < m; j++)
{
x = (i * m + j) * 4 + 4;
scanf("%d", &z);
add(x, x - 2, z);
scanf("%d", &z);
add(x, x - 1, z);
}
}
}

int dis[MAXN];
bool vis[MAXN];

void dijstra()
{
for (int i = S; i <= T; i++)
{
dis[i] = INF;
vis[i] = 0;
}
dis[S] = 0;

priority_queue<node> q;
q.push(node(S,0));
while (!q.empty())
{
int u = q.top().v;
q.pop();
if (u == T)
{
break;
}
if (vis[u])
{
continue;
}
vis[u] = true;
for (int i = head[u]; i != -1; i = e[i].next)
{
int v = e[i].v;
if (!vis[v] && dis[v] > dis[u] + e[i].w)
{
dis[v] = dis[u] + e[i].w;
q.push(node(v, dis[v]));
}
}
}

printf("%d\n", dis[T]);
}

int main()
{
while (~scanf("%d%d", &n, &m))
{
initGraph();
dijstra();
}

return 0;
}