'commit'

TangDou/Topic/P1364.cpp

@@ -0,0 +1,38 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 1000010;
+const int INF = 0x3f3f3f3f;
+
+int g[150][150];
+int w[N]; // 居民人口数，点权
+
+int main() {
+    int n;
+    cin >> n;
+
+    // 地图初始化
+    memset(g, 0x3f, sizeof g);
+    for (int i = 1; i <= n; i++) g[i][i] = 0;
+
+    for (int i = 1; i <= n; i++) {
+        int a, b;
+        cin >> w[i] >> a >> b; // w[i]:点权
+        g[i][a] = g[a][i] = 1; // i<->a无向边
+        g[i][b] = g[b][i] = 1; // i<->b无向边
+    }
+
+    // floyd
+    for (int k = 1; k <= n; k++)
+        for (int i = 1; i <= n; i++)
+            for (int j = 1; j <= n; j++)
+                if (g[i][j] > g[i][k] + g[k][j]) g[i][j] = g[i][k] + g[k][j];
+
+    int ans = INF;
+    for (int i = 1; i <= n; i++) { // 如果将医院设置在i处，那么计算一下它到各地的加权和
+        int s = 0;
+        for (int j = 1; j <= n; j++) s += w[j] * g[i][j];
+        ans = min(ans, s);
+    }
+    printf("%d", ans);
+    return 0;
+}

TangDou/Topic/【Floyd专题】.md

@@ -489,10 +489,50 @@ int main() {
 
 ```
 
-SSL-1761（城市问题）
-
 #### [$P1364$ 医院设置](https://www.luogu.com.cn/problem/P1364)
 
+```cpp {.line-numbers}
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 1000010;
+const int INF = 0x3f3f3f3f;
+
+int g[150][150];
+int w[N]; // 居民人口数，点权
+
+int main() {
+    int n;
+    cin >> n;
+
+    // 地图初始化
+    memset(g, 0x3f, sizeof g);
+    for (int i = 1; i <= n; i++) g[i][i] = 0;
+
+    for (int i = 1; i <= n; i++) {
+        int a, b;
+        cin >> w[i] >> a >> b; // w[i]:点权
+        g[i][a] = g[a][i] = 1; // i<->a无向边
+        g[i][b] = g[b][i] = 1; // i<->b无向边
+    }
+
+    // floyd
+    for (int k = 1; k <= n; k++)
+        for (int i = 1; i <= n; i++)
+            for (int j = 1; j <= n; j++)
+                if (g[i][j] > g[i][k] + g[k][j]) g[i][j] = g[i][k] + g[k][j];
+
+    int ans = INF;
+    for (int i = 1; i <= n; i++) { // 如果将医院设置在i处，那么计算一下它到各地的加权和
+        int s = 0;
+        for (int j = 1; j <= n; j++) s += w[j] * g[i][j];
+        ans = min(ans, s);
+    }
+    printf("%d", ans);
+    return 0;
+}
+```
+
 SSL-1613=CCF1342（最短路径问题）
+SSL-1761（城市问题）