Create 锯木厂选址_kedebug.cpp

From http://www.cnblogs.com/kedebug/archive/2013/03/02/2940423.html

CEOI/2004/锯木厂选址_kedebug.cpp

@@ -0,0 +1,54 @@
+/// Day2 : Two sawmills
+#include <iostream>
+#include <algorithm>
+#include <stdio.h>
+using namespace std;
+
+const int MAXN = 20010;
+const int INFS = 0x7fffffff;
+
+int w[MAXN], d[MAXN], x[MAXN], deq[MAXN];
+
+inline double slope(int i, int j)
+{
+    return 1.0 * (w[i] * x[i] - w[j] * x[j]) / (w[i] - w[j]);
+}
+
+int main()
+{
+    freopen("two.in","r",stdin);
+    freopen("two.out","w",stdout);
+
+    int n;
+    scanf("%d\n", &n);
+
+    for (int i = 1; i <= n; ++i)
+        scanf("%d %d", &w[i], &d[i]);
+
+    w[0] = d[0] = x[1] = 0;
+    int sum = 0;
+    for (int i = 1; i <= n; ++i)
+    {
+        x[i+1] = x[i] + d[i];
+        sum += x[i] * w[i], w[i] += w[i-1];
+    }
+
+    int ans = INFS;
+    int s = 0, e = -1;
+    for (int i = 1; i <= n; ++i)
+    {
+        while (s < e && slope(deq[e], deq[e-1]) >= slope(i, deq[e]))
+            --e;
+        deq[++e] = i;
+        while (s < e && slope(deq[s], deq[s+1]) <= x[i])
+            ++s;
+
+        int delta = -sum + w[i] * x[i] + (w[n] - w[i]) * x[n+1];
+        ans = min(ans, delta + w[deq[s]] * x[deq[s]] - x[i] * w[deq[s]]);
+    }
+    printf("%d\n", ans);
+
+    fclose(stdin);
+    fclose(stdout);
+    return 0;
+}