题目链接:https://pintia.cn/problem-sets/994805342720868352/problems/994805348471259136
题目大意:在用户点击第i个商品前,求出应该推荐的商品(最多k个)。
直接看代码吧
#include <bits/stdc++.h>
using namespace std;
const int N = 5e4 + 5;
int n, k, shu[N];
struct node {
int num, cnt;
node(int num = 0, int cnt = 0) {
this->num = num;
this->cnt = cnt;
}
bool operator < (const node &a) const {
return cnt != a.cnt ? cnt > a.cnt : num < a.num;
}
};
set<node> s;
int main() {
int x, count;
scanf("%d %d", &n, &k);
for(int i = 0; i < n; i++) {
scanf("%d", &x);
if(i) {
printf("%d:", x);
count = 0;
set<node>::iterator it;
for(it = s.begin(); it != s.end() && count < k; it++) {
printf(" %d", it->num);
count++;
}
printf("\n");
}
set<node>::iterator it = s.find(node(x, shu[x]));
if(it != s.end()) s.erase(it);
shu[x]++;
s.insert(node(x, shu[x]));
}
return 0;
}