骑士游历

http://codevs.cn/problem/1219/
此题，首先的想法是递归，但是不幸运的是超时了。
看了下题目的分类，找到了突破口。

#include<iostream>#include<stdio.h>#include<algorithm>using namespace std;int main(){    long long ditu[60][60] = {0};    int n, m, a, b, c, d;    cin >> n >> m >> a >> b >> c >> d;    ditu[a][b] = 1;    for (int i = a + 1; i <= c; i++)    for (int j = 1; j <= m; j++)    {        if (1 <= i - 2 && j + 1 <= m)            ditu[i][j] = ditu[i - 2][j + 1];        if (1 <= i - 2 && j - 1 >= 1)            ditu[i][j] += ditu[i - 2][j - 1];        if (1 <= i - 1 && j + 2 <= m)            ditu[i][j] += ditu[i - 1][j + 2];        if (1 <= i - 1 && j - 2 >= 1)            ditu[i][j] += ditu[i - 1][j - 2];    }    cout << ditu[c][d] << endl;    return 0;}