hdoj1428_漫步校园（dp）

#include<iostream>
#include<vector>
#include<string.h>
#include<queue>
#include<utility>
using namespace std;

int map[60][60];
int dir[4][2] = { { -1, 0 }, { 0, 1 }, { 1, 0 }, { 0, -1 } };
int len[60][60];
bool visited[60][60];
long long maxp[60][60];

void gplen(int n)
{
memset(visited, false, sizeof(visited));
queue<pair<int, int> > q;
while (!q.empty())
q.pop();
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
len[i][j] = 999999;
len[n - 1][n - 1] = map[n - 1][n - 1];
q.push(make_pair(n - 1, n - 1));
visited[n - 1][n - 1] = true;
while (!q.empty())
{
for (int i = 0; i < 4; i++)
{
int nx = q.front().first + dir[i][0];
int ny = q.front().second + dir[i][1];
if (nx >= 0 && nx < n&&ny >= 0 && ny<n)
{
if (len[nx][ny]>len[q.front().first][q.front().second] + map[nx][ny])
{
len[nx][ny] = len[q.front().first][q.front().second] + map[nx][ny];
if (!visited[nx][ny])
{
visited[nx][ny] = true;
q.push(make_pair(nx, ny));
}
}
}
}
visited[q.front().first][q.front().second] = false;
q.pop();
}
}

long long gmaxp(int x, int y, int n)
{
if (x == n - 1 && y == n - 1)
return 1;
for (int i = 0; i < 4; i++)
{
int nx = x + dir[i][0];
int ny = y + dir[i][1];
if (nx >= 0 && nx < n&&ny >= 0 && ny<n&&len[x][y]>len[nx][ny])
{
if (!visited[nx][ny])
{
maxp[nx][ny] = gmaxp(nx, ny, n);
visited[nx][ny] = true;
}
maxp[x][y] += maxp[nx][ny];
}
}
return maxp[x][y];
}

void solve(int n)
{
gplen(n);
memset(visited, false, sizeof(visited));
memset(maxp, 0, sizeof(maxp));
gmaxp(0, 0, n);
cout << maxp[0][0] << endl;
}

int main()
{
int n;
while (cin >> n)
{
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
cin >> map[i][j];
solve(n);
}
return 0;
}