POJ 1088 滑雪

经典DP。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,m,map[150][150],cnt=0,step[150][150];
int dx[]={0,0,1,0,-1},dy[]={0,1,0,-1,0};
struct pnt
{
    int x,y,val;
}p[10050];
bool cmp(pnt a,pnt b)
{
    return a.val>b.val;
}
void addpnt(int x,int y,int z)
{
    p[++cnt].x=x;
    p[cnt].y=y;
    p[cnt].val=z;
}
bool judge(int x,int y)
{
    if ((x>=1) && (x<=n) && (y>=1) && (y<=m))
        return true;
    return false;
}
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
        {
            scanf("%d",&map[i][j]);
            addpnt(i,j,map[i][j]);
        }
    sort(p+1,p+cnt+1,cmp);
    for (int i=1;i<=cnt;i++)
    {
        for (int j=1;j<=4;j++)
        {
            if ((judge(p[i].x+dx[j],p[i].y+dy[j])) && (map[p[i].x][p[i].y]>map[p[i].x+dx[j]][p[i].y+dy[j]]))
                step[p[i].x+dx[j]][p[i].y+dy[j]]=max(step[p[i].x+dx[j]][p[i].y+dy[j]],step[p[i].x][p[i].y]+1);
        }
    }
    int ans=0;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++) 
            ans=max(ans,step[i][j]);
    printf("%d
",ans+1);
    return 0;
}