Submission #835946

#	Time	Username	Problem	Language	Result	Execution time	Memory
835946		vjudge1	Bomb (IZhO17_bomb)	C++17	40 / 100	1090 ms	95564 KiB

bomb

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#include <bits/stdc++.h>

using namespace std;


const int N = 3e3 + 5;
int n, m;
int mp[N][N], pre[N][N];

bool bisa(int w, int h){
    int mpt[n + 1][m + 1];
    int sz = w*h;
    memset(mpt, 0, sizeof(mpt));
    for(int i = 1; i + w - 1 <= n; i++){
        for(int j = 1; j + h - 1 <= m; j++){
            int bi = i + w - 1, bj = j + h - 1;
            if(pre[bi][bj] + pre[i - 1][j - 1] - pre[i - 1][bj] - pre[bi][j - 1] == 0){
                mpt[i][j] = 1;
            }
        }
    }
    
    
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            mpt[i][j] += mpt[i][j - 1];
        }
    }
    
    for(int j = 1; j <= m; j++){
        for(int i = 1; i <= n; i++){
            mpt[i][j] += mpt[i - 1][j];
        }
    }
    
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            if(mp[i][j] == 0){
                int bi = max(i - w, 0);
                int bj = max(j - h, 0);
                if(mpt[i][j] + mpt[bi][bj] - mpt[bi][j] - mpt[i][bj] == 0){
                    return false;
                }
            }
        }
    }
    
    return true;
}

void solve(){
    cin >> n >> m;
    memset(mp, 0, sizeof(mp));
    memset(pre, 0, sizeof(pre));
    string s;
    int mw = n, cw = 0, mh = m, ch = 0;
    for(int i = 1; i <= n; i++){
        cin >> s;
        ch = 0;
        for(int j = 1; j <= m; j++){
            if(s[j - 1] == '0'){
                mp[i][j] = 1;
                if(ch != 0){
                    mh = min(mh, ch);
                }
                ch = 0;
            }else{
                ch++;
            }
        }
        if(ch != 0){
            mh = min(mh, ch);
        }
    }
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            pre[i][j] = pre[i][j - 1] + mp[i][j];
        }
    }
    
    for(int j = 1; j <= m; j++){
        cw = 0;
        for(int i = 1; i <= n; i++){
            pre[i][j] += pre[i - 1][j];
            if(mp[i][j] == 0){
                cw++;
            }else{
                if(cw != 0){
                    mw = min(mw, cw);
                }
                cw = 0;
            }
        }
        if(cw != 0){
            mw = min(mw, cw);
        }
    }
    int mx = 1;
    for(int i = 1; i <= mw; i++){
        int l = ceil((double)mx/i), r = mh;
        while(l <= r){
            int mid = (l + r)/2;
            if(bisa(i, mid)){
                l = mid + 1;
            }else{
                r = mid - 1;
            }
        }
        mx = max(mx, i*r);
    }
    cout << mx << endl;
    
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int t = 1;
    while(t--){
        solve();
    }

    return 0;
}

Compilation message (stderr)

bomb.cpp: In function 'bool bisa(int, int)':
bomb.cpp:20:9: warning: unused variable 'sz' [-Wunused-variable]
   20 |     int sz = w*h;
      |         ^~

• Subtask 1: 40 / 100