Submission #677846

#	Time	Username	Problem	Language	Result	Execution time	Memory
677846		qwerasdfzxcl	Seesaw (JOI22_seesaw)	C++17	1 / 100	176 ms	1364 KiB

seesaw

#include <bits/stdc++.h>

typedef long long ll;
using namespace std;
int dx[4] = {1, -1, 0, 0}, dy[4] = {0, 0, 1, -1};

struct DSU{
    int path[4004000], chk[4004000], n;
    vector<int> buf;
    void init(int _n){
        n = _n;
        for (int i=0;i<n*n;i++) path[i] = i, chk[i] = 0;
    }
    int find(int s){
        if (s==path[s]) return s;
        return path[s] = find(path[s]);
    }
    void merge(int s, int v){
        if (!chk[s] || !chk[v]) return;
        s = find(s), v = find(v);
        if (s==v) return;
        path[s] = v;
    }
    void on(int x, int y){
        int pos = (x-1)*n + y-1;

        if (x==y) pos = 0;

        chk[pos] = 1;
        buf.push_back(pos);

        for (int k=0;k<4;k++){
            int nx = x + dx[k], ny = y + dy[k];
            if (nx<=0 || nx>n || ny<=0 || ny>n || nx>ny) continue;
            int np = (nx-1)*n + ny-1;
            merge(pos, np);
        }
    }
    void off(){for (auto &x:buf){path[x] = x; chk[x] = 0;} buf.clear();}
    bool ok(){return find(0) == find(n-1) && chk[0] && chk[n-1];}
}dsu;

struct Frac{
    ll a, b;
    Frac(){}
    Frac(ll _a, ll _b): a(_a), b(_b) {}

    long double ch(){return (long double) a / b;}

    bool operator < (const Frac &F) const{
        return (__int128)a * F.b < (__int128)b * F.a;
    }
}val[2020][2020];
int n, a[2020];
Frac dp[2020][2020];

long double solve(int sx, int sy){
    for (int i=1;i<=n;i++) fill(dp[i]+1, dp[i]+n+1, Frac((ll)1e18, 1));
    dp[sx][sy] = val[sx][sy];

    Frac ret1 = dp[1][n], ret2 = dp[n][n];
    for (int d=sy-sx+1;d<=n-1;d++){
        for (int i=1;i<=n-d;i++){
            int j = i+d;
            if (val[i][j] < val[sx][sy]) continue;
            dp[i][j] = max(val[i][j], min(dp[i+1][j], dp[i][j-1]));
        }
    }

    ret1 = dp[1][n];

    for (int d=sy-sx-1;d>=0;d--){
        for (int i=1;i<=n-d;i++){
            int j = i+d;
            if (val[i][j] < val[sx][sy]) continue;
            dp[i][j] = max(val[i][j], min(dp[i-1][j], dp[i][j+1]));
            if (i==j) ret2 = min(ret2, dp[i][j]);
        }
    }

    auto ret = max(ret1, ret2);

    return ret.ch() - val[sx][sy].ch();
}

int main(){
    scanf("%d", &n);
    for (int i=1;i<=n;i++) scanf("%d", a+i);

    for (int i=1;i<=n;i++){
        val[i][i] = Frac(a[i], 1);
        for (int j=i+1;j<=n;j++){
            val[i][j].a = val[i][j-1].a + a[j];
            val[i][j].b = j-i+1;
            //printf("%Lf ", val[i][j].ch());
        }
        //printf("\n");
    }

    long double ans = 1e18;
    for (int i=1;i<=n;i++){
        for (int j=i+1;j<=n;j++) ans = min(ans, solve(i, j));
    }

    printf("%.15Lf\n", ans);
    return 0;
}

Compilation message (stderr)

seesaw.cpp: In function 'int main()':
seesaw.cpp:87:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
seesaw.cpp:88:33: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |     for (int i=1;i<=n;i++) scanf("%d", a+i);
      |                            ~~~~~^~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 0 / 33
• Subtask 3: 0 / 33
• Subtask 4: 0 / 33