80分求助

代码如下

#include<bits/stdc++.h>
using namespace std;
int r,c,minn=100100,ans=0;
int h[105][105];
int d[4][2]={{-1,0},{1,0},{0,-1},{0,1}};
void dfs(int x,int y,int step){
    //cout<<x<<" "<<y<<" "<<step<<endl;
    if(h[x][y]==minn){
        ans=max(ans,step+1);
        return;
    }
    int xx,yy;
    for(int i=0;i<4;i++){
        xx=x+d[i][0];
        yy=y+d[i][1];
        if(xx>=1&&xx<=r&&yy>=1&&yy<=c&&h[x][y]>h[xx][yy]){
            dfs(xx,yy,step+1);
        } 
    }
}
int main()
{
    cin>>r>>c;
    for(int i=1;i<=r;i++){
        for(int j=1;j<=c;j++){
            cin>>h[i][j];
            if(minn>h[i][j]) minn=h[i][j];
        }
    }
    for(int i=1;i<=r;i++){
        for(int j=1;j<=c;j++){
            dfs(i,j,0);
        }
    }
    cout<<ans<<endl;
    return 0;
}