uva116 - Unidirectional TSP(简单动规)

第二道动规题目，

这道题目卡了我很长时间的，就是因为字典序的问题我一直没想明白。

思路倒是不难，只要题目读懂了，这道题就能很容易的写出来代码。

代码如下：

#include <cstdio>
#define M 15
#define N 105
#define INF 0x7fffffff
int a[M][N], dp[M][N], pa[M][N];
int m, n;
void fun()
{
    for(int i = 0; i < m; i++)
    dp[i][n-1] = a[i][n-1];
    for(int y = n-2; y >= 0; y--)
    {
        for(int x = 0; x < m; x++)
        {
            int min = INF, minx = x;
            if(x>0&&x<m-1)
            {
                if(min>dp[(x-1+m)%m][y+1]){ min = dp[(x-1+m)%m][y+1]; minx = (x-1+m)%m; }
                if(min>dp[x][y+1]) { min = dp[x][y+1]; minx = x; }
                if(min>dp[(x+1)%m][y+1]) { min = dp[(x+1)%m][y+1]; minx = (x+1)%m; }
            }
            else if(x==0)
            {
                if(min>dp[x][y+1]) { min = dp[x][y+1]; minx = x; }
                if(min>dp[(x+1)%m][y+1]) { min = dp[(x+1)%m][y+1]; minx = (x+1)%m; }
                if(min>dp[(x-1+m)%m][y+1]){ min = dp[(x-1+m)%m][y+1]; minx = (x-1+m)%m; }
            }
            else
            {
                if(min>dp[(x+1)%m][y+1]) { min = dp[(x+1)%m][y+1]; minx = (x+1)%m; }
                if(min>dp[(x-1+m)%m][y+1]){ min = dp[(x-1+m)%m][y+1]; minx = (x-1+m)%m; }
                if(min>dp[x][y+1]) { min = dp[x][y+1]; minx = x; }
            }
            dp[x][y] = min+a[x][y];
            pa[x][y] = minx;
        }
    }
}
int main ()
{
    while(~scanf("%d %d",&m,&n))
    {
        for(int i = 0; i < m; i++)
            for(int j = 0; j < n; j++)
                scanf("%d",&a[i][j]);
        fun();
        int min = INF, minx;
        for(int i = 0; i < m; i++)
        {
            if(min>dp[i][0]){min = dp[i][0]; minx = i;}
        }
        for(int i = 0; i < n; i++)
        {
            if(i)   printf(" ");
            printf("%d",minx+1);
            minx = pa[minx][i];
        }
        printf("\n%d\n",min);
    }
    return 0;
}