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