期末预测之安全指数
实现
#include<bits/stdc++.h>
using namespace std;
int n;
int a,b;
int ans;
int main()
{
cin>>n;
while(n--)
{
scanf("%d%d",&a,&b);
ans+=(a*b);
}
cout<<max(0,ans);
}
期末预测之最佳阈值
思路
维护两个前缀和数组,分别是前i个中有多少个0和多少个1。
实现
#include<bits/stdc++.h>
#define x first
#define y second
using namespace std;
typedef pair<int, int> PII;
const int N = 100010;
int n;
PII q[N];
int s[2][N];
int main()
{
scanf("%d", &n);
for (int i = 1; i <= n; i ++ ) scanf("%d%d", &q[i].x, &q[i].y);
sort(q + 1, q + n + 1);
for (int i = 0; i < 2; i ++ )
for (int j = 1; j <= n; j ++ )
s[i][j] = s[i][j - 1] + (q[j].y == i);
int cnt = -1, res;
for (int i = 1; i <= n; i ++ )
{
int t = s[0][i - 1] + s[1][n] - s[1][i - 1];
if (t >= cnt) cnt = t, res = q[i].x;
while (i + 1 <= n && q[i + 1].x == q[i].x) i ++ ;
}
printf("%d\n", res);
return 0;
}