[HAOI2007]理想的正方形 单调队列 暴力

Posted 2021-01-18 guangheli

Code:

#include<cstdio>
#include<queue>
#include<algorithm>
using namespace std;
#define maxn 1002
#define ll long long
#define inf 100000000000
int minv[maxn][maxn], maxv[maxn][maxn];
struct Node{
    ll val;
    int pos;
    Node(ll val=0,int pos=0):val(val),pos(pos){}
};
deque<Node>Q[2];
int main(){
    //freopen("input.in","r",stdin);
    int a,b,n;
    ll ans=inf,p;
    scanf("%d%d%d",&a,&b,&n);
    for(int i=1;i<=a;++i){
        for(int j=1;j<=b;++j) {
            scanf("%lld",&p);
            while(!Q[0].empty()&&Q[0].front().pos<j-n+1)Q[0].pop_front();
            while(!Q[1].empty()&&Q[1].front().pos<j-n+1)Q[1].pop_front(); 
            while(!Q[0].empty()&&Q[0].back().val>=p) Q[0].pop_back();
            while(!Q[1].empty()&&Q[1].back().val<=p) Q[1].pop_back();
            Q[0].push_back(Node(p,j)),Q[1].push_back(Node(p,j));
            if(j>=n) minv[i][j]=Q[0].front().val, maxv[i][j]=Q[1].front().val;
        }
        while(!Q[0].empty())Q[0].pop_back();
        while(!Q[1].empty())Q[1].pop_back();
    }
    for(int i=n;i<=b;++i){
        for(int j=1;j<=a;++j){
            while(!Q[0].empty()&&Q[0].front().pos<j-n+1)Q[0].pop_front();
            while(!Q[1].empty()&&Q[1].front().pos<j-n+1)Q[1].pop_front(); 
            while(!Q[0].empty()&&Q[0].back().val>=minv[j][i]) Q[0].pop_back();
            while(!Q[1].empty()&&Q[1].back().val<=maxv[j][i]) Q[1].pop_back();
            Q[0].push_back(Node(minv[j][i],j)),Q[1].push_back(Node(maxv[j][i],j));
            if(j>=n) ans=min(ans,Q[1].front().val-Q[0].front().val);
        }
        while(!Q[0].empty())Q[0].pop_back();
        while(!Q[1].empty())Q[1].pop_back();
    }
    printf("%lld",ans);
    return 0;
}