PAT甲级真题 1034 Head of a Gang (30分)(用map数组模拟,注意测试点4)

题目

One way that the police finds the head of a gang is to check people’s phone calls. If there is a phone call between A and B, we say that A and B is related. The weight of a relation is defined to be the total time length of all the phone calls made between the two persons. A “Gang” is a cluster of more than 2 persons who are related to each other with total relation weight being greater than a given threshold K. In each gang, the one with maximum total weight is the head. Now given a list of phone calls, you are supposed to find the gangs and the heads.
Input Specification:
Each input file contains one test case. For each case, the first line contains two positive numbers N and K (both less than or equal to 1000), the number of phone calls and the weight threthold, respectively. Then N lines follow, each in the following format:
Name1 Name2 Time
where Name1 and Name2 are the names of people at the two ends of the call, and Time is the length of the call. A name is a string of three capital letters chosen from A-Z. A time length is a positive integer which is no more than 1000 minutes.
Output Specification:
For each test case, first print in a line the total number of gangs. Then for each gang, print in a line the name of the head and the total number of the members. It is guaranteed that the head is unique for each gang. The output must be sorted according to the alphabetical order of the names of the heads.
Sample Input 1:
8 59
AAA BBB 10
BBB AAA 20
AAA CCC 40
DDD EEE 5
EEE DDD 70
FFF GGG 30
GGG HHH 20
HHH FFF 10
Sample Output 1:
2
AAA 3
GGG 3
Sample Input 2:
8 70
AAA BBB 10
BBB AAA 20
AAA CCC 40
DDD EEE 5
EEE DDD 70
FFF GGG 30
GGG HHH 20
HHH FFF 10
Sample Output 2:
0

思路

map数组记录所有帮派,每个帮派以人名为key,以通话时间为value;每有一组通话,看双方是否已经属于某个帮派,若没有,则建立新的map加入二者,并将新map加入数组;若双方已属于某帮派,则累加双方在该map中的通话时长,注意若另一方是否也已属于另外一个帮派,则需将两个帮派合并,否则测试点4会报错。

测试点4测试用例:

7 59
AAA BBB 10
BBB AAA 20
AAA CCC 40
FFF GGG 30
GGG HHH 20
HHH FFF 10
AAA FFF 10

应输出:

1
AAA 6

最后遍历所有map,首先排除点元素数小于等于2的;然后累加所有元素值除以2(每个人的通话计算了2遍),即是总通话时长,若超过了K则属于帮派,其中值最大的就是boss,将boss名字和帮派人数加入组成结构体加入vector中;最后对vector按姓名排序即可。

柳神使用的方法是以人名为节点建立图,用dfs找出不同的连通分支即是各个帮派:1034. Head of a Gang (30)-PAT甲级真题(图的遍历dfs)

代码

#include 
#include 
#include 
#include 
using namespace std;

struct Head{
    string name;
    int num;
};
bool cmp(Head h1, Head h2){
    return h1.name < h2.name;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0); 

    int n, k;
    cin >> n >> k;
    vector<unordered_map<string, int> > m;
    for (int i=0; i<n; i++){
        string a, b;
        int t;
        cin >> a >> b >> t;
        bool found = false;
        for (int j=0; j<m.size(); j++) {
            if (m[j].find(a)!=m[j].end() || m[j].find(b)!=m[j].end()){
                //若两个帮派交叉则合并二者
                for (int k=j+1; k<m.size(); k++) {
                    if (m[k].find(a)!=m[k].end() || m[k].find(b)!=m[k].end()){
                        for (auto it=m[k].begin(); it!=m[k].end(); ++it){
                            m[j][it->first] += it->second;
                        }
                        m[k].clear();
                        break;
                    }
                }
                m[j][a] += t;
                m[j][b] += t;
                found = true;
                break;
            }
        }
        if (!found){
            unordered_map<string, int> tempMap;
            tempMap[a] = t;
            tempMap[b] = t;
            m.push_back(tempMap);
        }
    }

    vector<Head> h;
    for (int i=0; i<m.size(); i++){
        if (m[i].size() > 2){
            int total = 0;
            int maxT = 0; 
            string head = "";
            for (auto it=m[i].begin(); it!=m[i].end(); ++it){
                total += it->second;
                if (it->second > maxT){
                    maxT = it->second;
                    head = it->first;
                }
            }
            if (total/2 > k){  //每对通话时间统计了2次
                h.push_back({head, (int)m[i].size()});
            }
        }
    } 
    sort(h.begin(), h.end(), cmp);
    cout << h.size() << endl;
    for (int i=0; i<h.size(); i++){
        cout << h[i].name << " " << h[i].num << endl;
    } 
    return 0;
}

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