HDU 6015 Skip the Class 优先队列 map的使用

Skip the Class

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 1028 Accepted Submission(s): 599

Problem Description
Finally term begins. luras loves school so much as she could skip the class happily again.(wtf?)

Luras will take n lessons in sequence(in another word, to have a chance to skip xDDDD).

For every lesson, it has its own type and value to skip.

But the only thing to note here is that luras can’t skip the same type lesson more than twice.

Which means if she have escaped the class type twice, she has to take all other lessons of this type.

Now please answer the highest value luras can earn if she choose in the best way.

Input
The first line is an integer T which indicates the case number.

And as for each case, the first line is an integer n which indicates the number of lessons luras will take in sequence.

Then there are n lines, for each line, there is a string consists of letters from ‘a’ to ‘z’ which is within the length of 10,
and there is also an integer which is the value of this lesson.

The string indicates the lesson type and the same string stands for the same lesson type.

It is guaranteed that——

T is about 1000

For 100% cases, 1 <= n <= 100,1 <= |s| <= 10, 1 <= v <= 1000

Output
As for each case, you need to output a single line.
there should be 1 integer in the line which represents the highest value luras can earn if she choose in the best way.

Sample Input
2
5
english 1
english 2
english 3
math 10
cook 100
2
a 1
a 2

Sample Output
115
3

#include <iostream>
#include <map>
#include <string>
#include <cstdio>
#include <algorithm>

using namespace std;
typedef long long ll;
struct cla{
    char na[15];
    int val;
}a[105];
bool cmp(cla a,cla b) {
    return a.val>b.val;
}
int main() {
    int t;
    map<string,int> mp;
    cin>>t;
    while(t--) {
        mp.clear();
        int n;
        cin>>n;
        ll sum=0;
        for(int i=0;i<n;i++) {
            scanf("%s%d",a[i].na,&a[i].val);
        }
        sort(a,a+n,cmp);
        for(int i=0;i<n;i++) {
            if(mp[a[i].na]==2) continue;
            else mp[a[i].na]++;
            sum += a[i].val;
        }
        printf("%lld\n",sum); 
    }
    return 0;
} 
对于HDU4546问题,还可以使用优先队列(Priority Queue)来解决。以下是使用优先队列的解法思路: 1. 首先,将数组a进行排序,以便后续处理。 2. 创建一个优先队列(最小堆),用于存储组合之和的候选值。 3. 初始化优先队列,将初始情况(即前0个数的组合之和)加入队列。 4. 开始从1到n遍历数组a的元素,对于每个元素a[i],将当前队列中的所有候选值取出,分别加上a[i],然后再将加和的结果作为新的候选值加入队列。 5. 重复步骤4直到遍历完所有元素。 6. 当队列的大小超过k时,将队列中的最小值弹出。 7. 最后,队列中的所有候选值之和即为前k小的组合之和。 以下是使用优先队列解决HDU4546问题的代码示例: ```cpp #include <iostream> #include <vector> #include <queue> #include <functional> using namespace std; int main() { int n, k; cin >> n >> k; vector<int> a(n); for (int i = 0; i < n; i++) { cin >> a[i]; } sort(a.begin(), a.end()); // 对数组a进行排序 priority_queue<long long, vector<long long>, greater<long long>> pq; // 最小堆 pq.push(0); // 初始情况,前0个数的组合之和为0 for (int i = 0; i < n; i++) { long long num = pq.top(); // 取出当前队列中的最小值 pq.pop(); for (int j = i + 1; j <= n; j++) { pq.push(num + a[i]); // 将所有加和结果作为新的候选值加入队列 num += a[i]; } if (pq.size() > k) { pq.pop(); // 当队列大小超过k时,弹出最小值 } } long long sum = 0; while (!pq.empty()) { sum += pq.top(); // 求队列中所有候选值之和 pq.pop(); } cout << sum << endl; return 0; } ``` 使用优先队列的方法可以有效地找到前k小的组合之和,时间复杂度为O(nklog(k))。希望这个解法对你有所帮助!
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