UVA

几何专场中的一道题目

其实更是贪心

更定每一个圆后计算左右能覆盖的边界

然后贪心处理

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <string>#include <cmath>#include <set>#include <map>#include <stack>#include <queue>#include <ctype.h>#include <vector>#include <algorithm>#include <sstream>#define PI acos(-1.0)// cout << "  ===  " << endl;using namespace std;typedef long long ll;const int maxn = 10000 + 7, INF = 0x3f3f3f3f, mod = 1e9+7;int n, L, h;double c;struct node {    double o, r;    double l_, r_;}a[maxn];bool cmp(node a, node b) {    if(a.l_ == b.l_) return a.r_ < b.r_;    return a.l_ < b.l_;}void init() {    for(int i = 0; i < n; ++i) {        scanf("%lf%lf", &a[i].o, &a[i].r);        if(a[i].r <= c) {            a[i].l_ = a[i].r_ = 0;        }        else {            double t = sqrt((a[i].r)*(a[i].r) - (c)*(c));            a[i].l_ = a[i].o - t;            a[i].r_ = a[i].o + t;        }    }    sort(a, a+n, cmp);}void solve() {    double ansl = 0.0, ansr = 0.0;    if(a[0].l_ > ansl) { cout << -1 << endl; return; }    int i = 0, cnt = 0;    while(1) {         while(a[i].l_ <= ansl) {            ansr = max(ansr, a[i].r_);            i++;            if(i >= n) break;        }        cnt++;        if(ansr >= L) { cout << cnt << endl; return; }        if(ansl == ansr) { cout << -1 << endl; return; }        ansl = ansr;    }}int main() {    while(scanf("%d%d%d", &n, &L, &h) != EOF && n) {        c = (h/2.0);        init();        solve();    }    return 0;}