震惊！这么完美的代码居然WA了一半！

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;

struct p{
    int x,y,h;
    bool operator <(const p b) const{
        return this->h < b.h;
    }
}t;

int r,c,n,a,b,ans;
int f[101][101];
priority_queue <p,vector<p>,less<p> >q;

int maxn(int a,int b,int c,int d){
    return max(max(a,b),max(c,d));
}

int main(){
    ios::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
    cin>>r>>c;
    for(int i = 1; i <= r; ++i)
        for(int j = 1; j <= c; ++j){
            cin>>t.h;
            t.x = i,t.y = j;
            q.push(t);
        }
    for(int i = 1; i <= c*r; ++i){
        t = q.top();
        q.pop();
        a = t.x, b = t.y;
        f[a][b] = maxn(f[a-1][b],f[a][b-1],f[a+1][b],f[a][b+1])+1;
    }
    for(int i = 1; i <= r; ++i)
        for(int j = 1; j <= c; ++j)
            ans = max(ans,f[i][j]);
    cout<<ans<<endl;

    return 0;
}