• 576E


    咕咕咕


    容易想到用线段树分治。然而我不断 WA。这说明要写强力的 gen。

    有个问题就是一个边不能加入的时候,要改掉它的颜色,在后来仍然加入。

    #include <bits/stdc++.h>
    
    const int MAXN = 500010;
    int st[MAXN], ids[MAXN], top;
    struct dsu {
    	int idx;
    	int fa[MAXN], sz[MAXN]; bool fae[MAXN];
    	void init(int ix, int n) {
    		idx = ix;
    		for (int i = 1; i <= n; ++i) fa[i] = i, sz[i] = 1;
    	}
    	std::pair<int, int> find(int x) {
    		int res = 0;
    		while (x != fa[x]) res ^= fae[x], x = fa[x];
    		return std::make_pair(x, res);
    	}
    	void pop() {
    		int x = st[top], y = fa[x];
    		sz[y] -= sz[x]; fa[x] = x; fae[x] = 0;
    		--top;
    	}
    	bool link(int x, int y) {
    		int ex, ey;
    		std::tie(x, ex) = find(x);
    		std::tie(y, ey) = find(y);
    		if (x != y) {
    			if (sz[x] > sz[y]) std::swap(x, y);
    			st[++top] = x, ids[top] = idx;
    			fae[x] = ex ^ ey ^ 1;
    			sz[y] += sz[x];
    			fa[x] = y;
    			return true;
    		}
    		return (ex ^ ey) == 1;
    	}
    } ss[51];
    int n, m, K, Q;
    int xs[MAXN], ys[MAXN];
    int col[MAXN], lst[MAXN], disa[MAXN];
    const int MAXQ = MAXN * 50;
    struct qry { int id, c; } fir[MAXN];
    int qh[MAXN << 2], qn[MAXQ], qt[MAXQ], tot;
    int pre[MAXN], faqry[MAXN], elst[MAXN];
    int find(int x) { return x == faqry[x] ? x : faqry[x] = find(faqry[x]); }
    void addq(int u, int l, int r, int L, int R, int v) {
    	if (L <= l && r <= R) {
    		qn[++tot] = qh[u]; qt[qh[u] = tot] = v;
    		return ;
    	}
    	int mid = l + r >> 1;
    	if (L <= mid) addq(u << 1, l, mid, L, R, v);
    	if (mid < R) addq(u << 1 | 1, mid + 1, r, L, R, v);
    }
    void addq(int l, int r, int id) {
    	fir[l] = (qry) {id, col[id]}; faqry[l] = l;
    	pre[l] = elst[id]; elst[id] = l;
    	if (l + 1 <= r) addq(1, 1, Q, l + 1, r, l);
    }
    void solve(int u, int l, int r) {
    	int nowtop = top;
    	for (int i = qh[u]; i; i = qn[i]) {
    		const int v = find(qt[i]);
    		if (v) {
    			const qry t = fir[v];
    			ss[t.c].link(xs[t.id], ys[t.id]);
    		}
    	}
    	if (l == r) {
    		static qry t; t = fir[l];
    		disa[l] = !ss[t.c].link(xs[t.id], ys[t.id]);
    		if (disa[l]) faqry[l] = pre[faqry[l]];
    	} else {
    		int mid = l + r >> 1;
    		solve(u << 1, l, mid); solve(u << 1 | 1, mid + 1, r);
    	}
    	while (top > nowtop) ss[ids[top]].pop();
    }
    int main() {
    	std::ios_base::sync_with_stdio(false), std::cin.tie(0);
    	std::cin >> n >> m >> K >> Q;
    	for (int i = 1; i <= K; ++i) ss[i].init(i, n);
    	for (int i = 1; i <= m; ++i)
    		std::cin >> xs[i] >> ys[i];
    	for (int i = 1, e, v; i <= Q; ++i) {
    		std::cin >> e >> v;
    		if (col[e]) addq(lst[e], i - 1, e);
    		col[e] = v, lst[e] = i;
    	}
    	for (int i = 1; i <= m; ++i) if (col[i])
    		addq(lst[i], Q, i);
    	solve(1, 1, Q);
    	const char out[][10] = {"YES", "NO"};
    	for (int i = 1; i <= Q; ++i)
    		std::cout << out[disa[i]] << '
    ';
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/daklqw/p/12101344.html
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