HDU 4006 the kth great number (priority queue)

Priority queue header file

# Include <queue>

The default priority is from large to small.

Custom priority

 1 struct cmpmin{                         //按从小到大          2  3 // 因为标准库默认使用元素类型的<操作符来确定它们之间的优先级关系。 4     bool operator ()(int &a, int &b){ 5         return a>b;                       //所以规定小的元素的优先级大于大的元素。  6     } 7 }; 8  9 struct cmpmax{                        //按从大到小          10     bool operator ()(int &a, int &b){11         return a<b;                       12     }13 };14 15 16 //多个元素的时候 17 struct node{      18     int x, y;19     friend bool operator <(int a, int b){        //小的优先级小，所以按照x从大到小，注意默认是<来确定优先级。 20         return a.x < b.x;21     }22 }23 24 struct node{25     int x, y;26     friend bool operator <(int a, int b){        //小的优先级大，所以按照x从小到大 27         return a.x > b.x;                       28     }29 }

View code

 

This topic outputs the k-th largest number. Because the data volume is large and cannot be sorted each time, the priority queue is used to solve the problem.

 1 #include <iostream> 2 #include <cstdio> 3 #include <vector> 4 #include <queue> 5 using namespace std; 6 struct cmp{ 7     bool operator ()(int &a,int &b){ 8         return a>b;//最小值优先 9     }10 };11 int n, k, val, cnt;12 char c;13 int main(){14     while(~scanf("%d%d", &n, &k)){15         cnt = 0;16         priority_queue <int, vector<int>,cmp> q;17         while(n--){18             cin>>c;19             if(c == ‘Q‘){20                 printf("%d\n", q.top());21             }22             else if(c == ‘I‘){23                 scanf("%d", &val);24                 if(cnt < k){25                     q.push(val);cnt++;26                 }27                 else{28                     if(val > q.top()){29                         q.pop();30                         q.push(val);31                     }32                 }33             }34         }35         36     }37     38     39     return 0;40 }

 

HDU 4006 the kth great number (priority queue)