题解 |

A

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 50;
struct node {
	int x, r;
	int l, R;
}a[N];
bool cmp(node an, node bn) {
	return an.l < bn.l;
}
int main()
{
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i].x >> a[i].r;
		a[i].R = a[i].x + a[i].r;
		a[i].l = a[i].x - a[i].r;
	}
	sort(a + 1, a + n + 1, cmp);
	long long ans = 0;
	   int end = a[1].R;
		for (int i = 2; i <= n; i++)
		{
			if (a[i].l > end)
			{
				ans += (a[i].l - end);
				end = a[i].R;
			}
			else {
				if (end < a[i].R) {
					end = a[i].R;
				}
			}
		}
	
	cout << ans << endl;
	return 0;
}

G

// 1 616
// 
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main()
{
	string a;
	cin >> a;
	int idx = 0;

	if (a[0] == '9') {
		int flag = 0;
		for (int i = 0; i < a.size() - 1 ; i++) {
			if (a[i] != '9') {
				flag = 1;
				break;
			}
		}
		if (flag == 0) {
			cout << a;
		}
		else {
				for (int i = 1; i <= a.size() - 1 ; i++) {
					cout << 9;
				}
		}
	}
	else {
		if (a == "1" || a == "2" || a == "3" || a == "4" || a == "5" || a == "6" || a == "7" || a == "8" || a == "9") {
			cout << a;
		}
		else {
			for (int i = 1; i <= a.size() - 1; i++) {
				cout << "9";
			}
		}
	}
	return 0;
}

D

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 50;
const double pi = acos(-1);
int main()
{
	int t;
	cin >> t;
	while (t--) {
		double r;
		cin >> r;
		double x, y, d;
		cin >> x >> y >> d;
		double dis = sqrt(x * x + y * y);
		double a_x = dis - d;
		double b_x = dis + d;
		// 两侧
		if (a_x * b_x < 0) {
			double jd1 = acos(fabs(a_x) / r);
			//jd1  =  arccos(a_x/r) 
			double jd2 = acos(fabs(b_x) / r);
			double jd = pi - jd1 - jd2;
			printf("%.12f\n", jd * r);
		}
		else if (a_x < 0 && b_x <= 0) {
			// 一侧
			double jd2 = acos(fabs(b_x) / r);
			double jd1 = acos(fabs(a_x) / r);
			double jd = abs(jd1 - jd2);
			printf("%.12f\n", jd * r);
		}
		else {
			double jd2 = acos(fabs(b_x) / r);
			double jd1 = acos(fabs(a_x) / r);
			double jd = abs(jd1 - jd2);
			printf("%.12f\n", jd * r);
		}
	}
	return 0;
}