From 334ce6d602b385dabafd8d12374efcf827b7e318 Mon Sep 17 00:00:00 2001
From: Anthony Wang
Date: Fri, 12 Mar 2021 20:59:30 -0600
Subject: Add minimizing.cpp

---
 21/feb/plat/minimizing.cpp | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 21/feb/plat/minimizing.cpp

diff --git a/21/feb/plat/minimizing.cpp b/21/feb/plat/minimizing.cpp
new file mode 100644
index 0000000..9d5bf95
--- /dev/null
+++ b/21/feb/plat/minimizing.cpp
@@ -0,0 +1,78 @@
+#include <bits/stdc++.h>
+#define f first
+#define s second
+using namespace std;
+using ll = long long;
+using ii = pair<int, int>;
+constexpr int MX = 1e5+5;
+
+int ans, D[2*MX];
+vector<int> G[MX], H[2*MX];
+
+int main() {
+	if (fopen("in", "r")) freopen("in", "r", stdin), freopen("out", "w", stdout);
+	cin.tie(0)->sync_with_stdio(0);
+
+	int T; cin >> T;
+	while (T--) {
+		int N, M; cin >> N >> M;
+		for (int u = 1; u <= N; ++u) G[u].clear();
+		for (int u = 1; u <= 2*N; ++u) H[u].clear();
+		for (int i = 0; i < M; ++i) {
+			int x, y; cin >> x >> y;
+			G[x].push_back(y), G[y].push_back(x);
+			H[x].push_back(y+N), H[y+N].push_back(x);
+			H[y].push_back(x+N), H[x+N].push_back(y);
+		}
+		
+		for (int u = 1; u <= 2*N; ++u) D[u] = 1e9;
+		queue<int> q;
+		D[1] = 0, q.push(1);
+		while (q.size()) {
+			int u = q.front(); q.pop();
+			for (int v : H[u]) if (D[v] == 1e9)
+				D[v] = D[u]+1, q.push(v);
+		}
+
+		if (*max_element(D+1, D+2*N+1) == 1e9) {
+			cout << N-1 << '\n';
+			continue;
+		}
+
+		/*vector<ii> C;
+		C.emplace_back(0, 0);
+		for (int u = 1; u <= N; ++u) {
+			C.emplace_back(D[u], D[u+N]);
+		}*/
+
+		ans = 0;
+		map<ii, int> f;
+		map<ii, vector<int>> b;
+		for (int u = 1; u <= N; ++u) {
+			ii p(min(D[u], D[u+N]), max(D[u], D[u+N]));
+			++f[p], b[p].push_back(u);
+		}
+		map<ii, int> ea;
+		for (auto [p, c] : f) {
+			int pr = ea[ii(p.f-1, p.s+1)];
+			if (p.f+1 == p.s) {
+				if (p.f == 0) ans += (c+1)/2;
+				else if (f[ii(p.f-1, p.s-1)]) ans += max((c-pr)+(pr+1)/2, (c+1)/2);
+				else {
+					if (pr < c) ans += c-pr;
+					ans += (c+1)/2;
+				}
+			}
+			else {
+				ans += c;
+				if (p.f == 0) ea[p] = c;
+				else if (f[ii(p.f-1, p.s-1)]) ea[p] += min(c, pr);
+				else {
+					if (pr < c) ans += c-pr;
+					ea[p] = c;
+				}
+			}
+		}
+		cout << ans << '\n';
+	}
+}
-- 
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