UVALive 6953 Digi Comp II

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拓扑排序，顺便记录一下答案

#include<cstdio>
#include<ctime>
#include<queue>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long LL;
const int maxn = 500015;
LL n, sum[maxn], T, m, flag[maxn], in[maxn];
int L[maxn], R[maxn];
char s[8];

int main()
{
	while (cin >> n >> m)
	{
		for (int i = 0; i <= m; i++) sum[i] = in[i] = 0;
		for (int i = 1; i <= m; i++)
		{
			scanf("%s%d%d", s, &L[i], &R[i]);
			flag[i] = s[0] == 'L' ? 1 : 0;
			++in[L[i]];	++in[R[i]];
		}
		queue<int> p;
		for (int i = 1; i <= m; i++) if (!in[i]) p.push(i);
		sum[1] = n;
		while (!p.empty())
		{
			int q = p.front();	p.pop();
			if (L[q])
			{
				if (--in[L[q]] == 0) p.push(L[q]);
				sum[L[q]] += (sum[q] + flag[q]) >> 1;
			}
			if (R[q])
			{
				if (--in[R[q]] == 0) p.push(R[q]);
				sum[R[q]] += (sum[q] + 1 - flag[q]) >> 1;
			}
			flag[q] ^= (sum[q] & 1);
		}
		for (int i = 1; i <= m; i++)
			if (flag[i]) putchar('L'); else putchar('R');
		putchar(10);
	}
	return 0;
}