【洛谷】P10417 [蓝桥杯 2023 国 A] 第 K 小的和 的题解

【洛谷】P10417 [蓝桥杯 2023 国 A] 第 K 小的和 的题解

题目传送门

题解

CSP-S1 补全程序，致敬全 A 的答案，和神奇的预言家。

写一下这篇的题解说不定能加 CSP 2024 的 RP

代码

#include <bits/stdc++.h>
#define lowbit(x) x & (-x)
#define endl "\n"
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define int long long
namespace fastIO {
	inline int read() {
		register int x = 0, f = 1;
		register char c = getchar();
		while (c < '0' || c > '9') {
			if(c == '-') f = -1;
			c = getchar();
		}
		while (c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
		return x * f;
	}
	inline void write(int x) {
		if(x < 0) putchar('-'), x = -x;
		if(x > 9) write(x / 10);
		putchar(x % 10 + '0');
		return;
	}
}
using namespace fastIO;
int n, m, k, a[100005], b[100005]; 
bool check (int x) {
	int res = 0;
	for (int i = 1; i <= n; i++) {
		res += upper_bound (b + 1, b + m + 1, x - a[i]) - b - 1;
	}
	return res >= k;
}
signed main() {
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	n = read(), m = read(), k = read();
	for(int i = 1; i <= n; i ++) {
		a[i] = read();
	}
	for(int i = 1; i <= m; i ++) {
		b[i] = read();
	}
	sort(b + 1, b + m + 1);
	int l = 0, r = INT_MAX;
	while (l < r) {
		int mid = (l + r) >> 1;
		if (check (mid)) {
			r = mid;
		}
		else l = mid + 1;
	}
	write(l);
	return 0;
}