USACO Section 1.3 Greedy Algorithm

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两道贪心题，刷水题完全没有成就感，更不用说刷水题还一直wa了 Orz

Mixing Milk

按照农夫提供的牛奶价格 sort一遍农夫，贪心

#include <bits/stdc++.h>using namespace std;struct Farmer {  int p, w;  void read() {    scanf("%d %d", &p, &w);  }  bool operator < (const Farmer & b) const {    return p < b.p;  }} a[5005];int main() {  freopen("milk.in", "r", stdin);  freopen("milk.out", "w", stdout);  int n, m;  scanf("%d %d", &n, &m);  for (int i = 0; i < m; i++) a[i].read();  sort(a, a + m);  int t = n, ans = 0;  for (int i = 0; i < m && t; i++) {    int b = min(t, a[i].w);    t -= b; ans += b * a[i].p;  }  printf("%d\n", ans);}

Barn repairing

sort 相邻两个有牛的牛棚的间距进行贪心，这题我没考虑到 m 的值可能能大于有牛的牛棚数量，更无奈的是之前的程序在我本地的 C++ 11 版本的运行结果是正确的，导致一直debug无果，幸好后来反应过来，不过也算是栽在了水题上面了，还是太弱啊 ...

#include <bits/stdc++.h>using namespace std;int a[222], b[222];int main() {  freopen("barn1.in", "r", stdin);  freopen("barn1.out", "w", stdout);  int n, m, c;  scanf("%d %d %d", &m, &c, &n);  for (int i = 0; i < n; i++) scanf("%d", a + i);  sort(a, a + n);  n--;  for (int i = 0; i < n; i++) b[i] = a[i + 1] - a[i] - 1;  sort(b, b + n);  int ans = a[n] - a[0] + 1;  for (int i = 1; i < m && n - i >= 0; i++) ans -= b[n - i];  printf("%d\n", ans);}

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