无语了，90分，还是第一个点错的，咋地了

#include<iostream>
#include<cstdio>
using namespace std;
int dx[5]={0,-1,0,1,0},
    dy[5]={0,0,1,0,-1};
long r,c,i,j,p,t,ans;
long m[101][101],f[101][101];
int search(int,int);
int main(){
    cin>>r>>c;
    ans=0;
    for (i=1;i<=r;i++)
        for (j=1;j<=c;j++)
            cin>>m[i][j];
    for (i=1;i<=r;i++)
        for (j=1;j<=c;j++){
            t=search(i,j);
            f[i][j]=t;
            if (t>ans) ans=t;
        }
    cout<<ans;
}
int search(int x,int y){
    int i,j,tmp,nx,ny;
    if (f[x][y]>0) return (f[x][y]);
    t=1;
    for (i=1;i<=4;i++){
        nx=x+dx[i];
        ny=y+dy[i];
        if ((nx>=1) && (nx<=r) && (ny>=1) && (ny<=c) && (m[x][y]<m[nx][ny])){
            tmp=search(nx,ny)+1;
            if (tmp>t) t=tmp;
        }
    }
    f[x][y]=t;
    return(t);
}