47 lines
1.0 KiB
C++
47 lines
1.0 KiB
C++
#include <iostream>
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#include <tuple>
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#include <vector>
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#include <iomanip>
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#include <algorithm>
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using namespace std;
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struct cmp {
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bool operator()(const tuple<double, double, double>& a,
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const tuple<double, double, double>& b) const {
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return get<2>(a) > get<2>(b); // 按性价比降序
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}
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};
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int main() {
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int n;
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double t;
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cin >> n >> t;
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vector<tuple<double, double, double>> arr(n);
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for (int i = 0; i < n; i++) {
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double a, b;
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cin >> a >> b;
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arr[i] = make_tuple(a, b, b / a); // (重量, 价值, 单位价值)
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}
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sort(arr.begin(), arr.end(), cmp());
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double value = 0;
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int p = 0;
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while (t > 0 && p < n) {
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if (t >= get<0>(arr[p])) {
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value += get<1>(arr[p]); // 取整个物品
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t -= get<0>(arr[p]); // 先减当前重量
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p++;
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} else {
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value += t * get<2>(arr[p]); // 取一部分
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break;
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}
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}
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cout << fixed << setprecision(2) << value << endl;
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return 0;
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}
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