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;
}