Submission #475208

#	Time	Username	Problem	Language	Result	Execution time	Memory
475208		khr03ae	Circle selection (APIO18_circle_selection)	C++14	0 / 100	359 ms	32676 KiB

circle_selection

#include <bits/stdc++.h>

using namespace std;

typedef long long i64;

const int MAX = 3e5 + 9;
int N, par[MAX];
bool removed[MAX];

struct Circle {
    i64 x, y;
    i64 radius;
    int index;
} circles[MAX], sweep[MAX];

pair<int, int> seg[MAX];

bool cmpX(Circle& a, Circle& b) {
    if (a.x == b.x) return a.radius > b.radius;
    return a.x < b.x;
}

bool intercept(Circle& a, Circle& b) {
    i64 dx = a.x - b.x;
    i64 dy = a.y - b.y;
    i64 dist2 = dx * dx * 1LL + dy * dy * 1LL;
    i64 r2 = (a.radius * 1LL + b.radius * 1LL) * (a.radius * 1LL + b.radius * 1LL) * 1LL;
    if (dist2 <= r2) {
        return true;
    }  else {
        return false;
    }
}

int find_intercept_left(Circle& rhs, int low, int high) {
    if (low == high)
        return low;
    int mid = (low + high)  / 2;
    if (intercept(rhs, sweep[mid])) {
        return find_intercept_left(rhs, low, mid); 
    } else {
        return find_intercept_left(rhs, mid + 1, high);
    }
}

int find_intercept_right(Circle& rhs, int low, int high) {
    if (low == high)
        return low;
    int mid = (low + high + 1) / 2;
    if (intercept(rhs, sweep[mid])) {
        return find_intercept_right(rhs, mid, high); 
    } else {
        return find_intercept_right(rhs, low, mid - 1);
    }
}

bool cmp(Circle& a, Circle& b) {
    if (a.radius == b.radius)
        return a.x < b.x;
    return a.radius > b.radius;
}

int main() {
    scanf("%d", &N);
    for (int i = 0; i < N; ++i) {
        scanf("%lld%lld%lld", &circles[i].x, &circles[i].y, &circles[i].radius);
        circles[i].index = i;
    }
    for (int i = 0; i < N; ++i)
        sweep[i] = circles[i];
    sort(sweep, sweep + N, cmpX);
    for (int i = 0; i < N; ++i) {
        int u = sweep[i].index;
        if (i == 0) {
            seg[u].first = i;
            seg[u].second = find_intercept_right(sweep[i], i, N - 1);
        } else if (i == N - 1) {
            seg[u].first = find_intercept_left(sweep[i], 0, i);
            seg[u].second = N - 1;
        } else {
            seg[u].first = find_intercept_left(sweep[i], 0, i);
            seg[u].second = find_intercept_right(sweep[i], i, N - 1);
        }
    }
    // for (int i = 0; i < N; ++i) {
    //     printf("%d/%d/%d ", sweep[i].index + 1, seg[i].first, seg[i].second);
    // }
    // printf("\n");
    sort(circles, circles + N, cmp);
    for (int i = 0; i < N; ++i)
        removed[i] = false;
    for (int i = 0; i < N; ++i) {
        int u = circles[i].index;
        if (removed[u])
            continue;
        par[u] = u;
        for (int j = seg[u].first; j <= seg[u].second; ++j) {
            int v = sweep[j].index;
            if (removed[v])
                continue;
            par[v] = u;
            removed[v] = true;
        }
        removed[u] = true;
    }
    for (int i = 0; i < N; ++i) {
        printf("%d ", par[i] + 1);
    }
    printf("\n");
}

Compilation message (stderr)

circle_selection.cpp: In function 'int main()':
circle_selection.cpp:65:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     scanf("%d", &N);
      |     ~~~~~^~~~~~~~~~
circle_selection.cpp:67:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |         scanf("%lld%lld%lld", &circles[i].x, &circles[i].y, &circles[i].radius);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 7
• Subtask 2: 0 / 12
• Subtask 3: 0 / 15
• Subtask 4: 0 / 23
• Subtask 5: 0 / 30
• Subtask 6: 0 / 13