【Poj1088 滑雪】記憶化搜索

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int MAXN = 105;
int a[MAXN][MAXN], rem[MAXN][MAXN];
int r, c;
int dirx[] = {-1, 1, 0, 0}, diry[] = {0, 0, -1, 1};

int dfs(int x, int y)
{
    if (rem[x][y] != -1)
    {
        return rem[x][y];
    }

    rem[x][y] = 1;

    for (int i = 0; i < 4; i++) //這裏一定是從0開始
    {
        int nx = x + dirx[i];
        int ny = y + diry[i];
        if (nx < 1 || ny < 1 || nx > r || ny > c)
        {
            continue;
        }
        else if (a[x][y] <= a[nx][ny])
        {
            continue;
        }
        rem[x][y] = max(rem[x][y], dfs(nx, ny) + 1);
    }
    return rem[x][y];
}

int main()
{
    int sum = 0;
    scanf("%d %d", &r, &c);
    for (int i = 1; i <= r; i++)
    {
        for (int j = 1; j <= c; j++)
        {
            scanf("%d", &a[i][j]);
        }
    }

    memset(rem, -1, sizeof(rem));

    for (int i = 1; i <= r; i++)
    {
        for (int j = 1; j <= c; j++)
        {
            rem[i][j] = max(rem[i][j], dfs(i, j));
            if (rem[i][j] > sum)
            {
                sum = rem[i][j];
            }
        }
    }
    printf("%d\n", sum);
    return 0;
}

一開始WA，後來發現dirx和diry這兩個數組都是從0開始存的，所以要從0開始循環，以後要注意。