From d3eb18bfddb90192f64faafe73324161debfdc45 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Sun, 24 Jul 2022 20:45:05 +0800
Subject: [PATCH] =?UTF-8?q?P3645=20[APIO2015]=20=E9=9B=85=E5=8A=A0?=
 =?UTF-8?q?=E8=BE=BE=E7=9A=84=E6=91=A9=E5=A4=A9=E6=A5=BC?=
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https://www.luogu.com.cn/record/81011789
---
 Luogu/P3645/P3645.cpp | 94 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 Luogu/P3645/P3645.cpp

diff --git a/Luogu/P3645/P3645.cpp b/Luogu/P3645/P3645.cpp
new file mode 100644
index 00000000..cd3a8fd2
--- /dev/null
+++ b/Luogu/P3645/P3645.cpp
@@ -0,0 +1,94 @@
+#include <iostream>
+#include <bitset>
+#include <cmath>
+#include <cstring>
+#include <queue>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 30001;
+
+int n, m, l, s, t;
+std::vector<std::pair<int, short>> g[N * 101];
+int dist[N * 101];
+std::bitset<N * 101> vis;
+
+int spfa() {
+    memset(dist, 0x3f, sizeof(dist));
+    std::queue<int> q;
+
+    dist[s] = 0;
+    q.push(s);
+    vis[s] = true;
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        vis[u] = false;
+
+        for (auto t : g[u]) {
+            int v = t.first;
+            short w = t.second;
+
+            if (dist[v] > dist[u] + w) {
+                dist[v] = dist[u] + w;
+
+                if (!vis[v]) {
+                    q.push(v);
+                    vis[v] = true;
+                }
+            }
+        }
+    }
+
+    return dist[t] == 0x3f3f3f3f ? -1 : dist[t];
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    l = std::min(static_cast<int>(std::sqrt(n)), 100);
+
+    for (int i = 1, b, p; i <= m; i++) {
+        cin >> b >> p;
+
+        b++;
+
+        if (i == 1) s = b;
+        if (i == 2) t = b;
+
+        if (p <= l) {
+            g[b].emplace_back(p * n + b, 0);
+        } else {
+            for (int j = 1; b + j * p <= n; j++) {
+                g[b].emplace_back(b + j * p, j);
+            }
+
+            for (int j = 1; b - j * p > 0; j++) {
+                g[b].emplace_back(b - j * p, j);
+            }
+        }
+    }
+
+    for (int i = 1; i <= l; i++) {
+        for (int j = 1; j <= n; j++) {
+            g[i * n + j].emplace_back(j, 0);
+        }
+
+        for (int j = 1; j <= n - i; j++) {
+            g[i * n + j].emplace_back(i * n + j + i, 1);
+            g[i * n + j + i].emplace_back(i * n + j, 1);
+        }
+    }
+
+    cout << spfa() << endl;
+
+    return 0;
+}