CF922D Robot Vacuum Cleaner 贪心+排序

正确的贪心方法：按照比例排序.

code:

#include <bits/stdc++.h>
#define N 200000
#define ll long long
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
int n;
char str[N],S[N];
struct Node
{
    int l,r;
    double perc;
}t[N];
bool cmp(Node a,Node b)
{
    return a.perc>b.perc;
}
int main()
{
    int i,j,cnt=0;
    // msetIO("input");
    scanf("%d",&n);
    for(i=1;i<=n;++i)
    {
        scanf("%s",str+1);
        int len=strlen(str+1),s=0;
        t[i].l=cnt+1;
        for(j=1;j<=len;++j) ++cnt, S[cnt]=str[j],s+=(str[j]=='s');
        t[i].r=cnt;
        t[i].perc=(double)s/len;
    }
    ll pre=0,ans=0;
    sort(t+1,t+1+n,cmp);
    for(i=1;i<=n;++i)
    {
        int l=t[i].l;
        int r=t[i].r;
        for(j=l;j<=r;++j)
        {
            if(S[j]=='s')
            {
                ++pre;
            }
            else
            {
                ans+=pre;
            }
        }
    }
    printf("%lld\n",ans);
    return 0;
}