2019CCSP A. 摘水果（拓扑排序）

看到数据量1e2，直接暴力即可。每一轮暴力检查两棵树上度为0的点，寻找最优答案输出，同时更新deg数组。

#include <bits/stdc++.h>
#define N 405
#define M 10005
using namespace std;
int n, head[N], ver[2 * M], Next[2 * M], tot = 0, deg[N], a[2 * N], b[2 * N];
void add(int x, int y) {
	ver[++tot] = y, Next[tot] = head[x], head[x] = tot;
}
bool chosen[N];
int main() {
	memset(deg, 0, sizeof(deg));
	cin >> n;
	for(int i = 1; i <= 2 * n; i++) {
		cin >> a[i];
	}
	for(int i = 1; i <= 2 * n; i++) {
		cin >> b[i];
		add(i, b[i]);
		deg[b[i]]++;
	}
	for(int t = 1; t <= n; t++) {
		int val = 0, aa = 0, id1 = 0, id2 = 0;
		for(int i = 1; i <= n; i++) {
			for(int j = n + 1; j <= 2 * n; j++) {
				if(!(deg[i] == 0 && deg[j] == 0 && chosen[i] == 0 && chosen[j] == 0)) 			continue;
				int tmp = a[i] ^ a[j];
				if(tmp > val) {
					val = tmp;
					aa = a[i];
					id1 = i;
					id2 = j;
				} else if(tmp == val) {
					if(a[i] > aa) {
						aa = a[i];
						id1 = i;
						id2 = j;
					} else if(a[i] == aa) {
						if(i > id1) {
							id1 = i;
							id2 = j;
						} else if(i == id1) {
							if(j > id2) {
								id2 = j;
							}
						}
					}
				}
			}
		}
		cout << val << (t == n ? "" : " ");
		//cout << id1 << " " << id2 << endl;
		chosen[id1] = chosen[id2] = 1;
		for(int i = head[id1]; i; i = Next[i]) {
			int y = ver[i];
			if(deg[y]) deg[y]--;
		}
		for(int i = head[id2]; i; i = Next[i]) {
			int y = ver[i];
			if(deg[y]) deg[y]--;
		}
	}
}
// 3              
// 3 9 4 1 3 4
// 0 0 2 0 4 4

标签：aa,2019CCSP,int,拓扑,id2,tot,id1,排序,deg
来源： https://www.cnblogs.com/lipoicyclic/p/15409940.html