Submission #936112

#	Time	Username	Problem	Language	Result	Execution time	Memory
936112		guagua0407	Bomb (IZhO17_bomb)	C++17	40 / 100	1103 ms	43700 KiB

bomb

#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define f first
#define s second
#define all(x) x.begin(),x.end()

const int mxn=2505;
char c[mxn][mxn];
int pre[mxn][mxn];
bool used[mxn][mxn];
int mn[mxn];
int n,m;

bool check(int x,int y){
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            used[i][j]=false;
        }
    }
    for(int j=1;j<=m;j++){
        mn[j]=0;
    }
    int cur=0;
    for(int i=y;i<=n;i++){
        int prv=0;
        for(int j=x;j<=m;j++){
            int sum=pre[i][j]-pre[i][j-x]-pre[i-y][j]+pre[i-y][j-x];
            if(sum!=x*y){
                continue;
            }
            for(int k=max(prv+1,j-x+1);k<=j;k++){
                for(int l=i;l>=max(mn[k]+1,i-y+1);l--){
                    used[l][k]=true;
                    cur++;
                }
                mn[k]=i;
            }
            prv=j;
        }
    }
    return cur==pre[n][m];
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    auto st=clock();
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>c[i][j];
            pre[i][j]=pre[i][j-1]+pre[i-1][j]-pre[i-1][j-1]+(c[i][j]=='1');
        }
    }
    int ans=1;
    set<int> S;
    for(int len=m;len>=1;len--){
        int r=(ans+len-1)/len;
        while(r<=n and check(len,r)){
            r++;
        }
        S.insert(r);
        ans=max(ans,len*(r-1));
    }
    assert(S.size()<100);
    cout<<ans<<'\n';
}

Compilation message (stderr)

bomb.cpp: In function 'int main()':
bomb.cpp:49:10: warning: unused variable 'st' [-Wunused-variable]
   49 |     auto st=clock();
      |          ^~

• Subtask 1: 40 / 100