非常直接的记搜
#include <bits/stdc++.h>
using namespace std;
const int N = 310;
int a[N][N], mx[N][N];
int n, m;
pair<int, int> dir[4] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
int dfs(int r, int c) {
if (mx[r][c] == -1) {
mx[r][c] = 1;
for (int i = 0; i < 4; i++) {
int r1 = r + dir[i].first, c1 = c + dir[i].second;
if (a[r][c] > a[r1][c1]) {
mx[r][c] = max(mx[r][c], 1 + dfs(r1, c1));
}
}
}
return mx[r][c];
}
int main () {
cin >> n >> m;
memset(a, 0x3f, sizeof a);
memset(mx, -1, sizeof mx);
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
int ans = -1;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (mx[i][j] == -1) {
ans = max(ans, dfs(i, j));
}
}
}
cout << ans << endl;
return 0;
}