USACO 2014 US Open Fair Photography /// 技巧

#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define INF 0x3f3f3f3f
#define mem(i,j) memset(i,j,sizeof(i))
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,r,l) for(int i=r;i>=l;i--)
#define gcd(i,j) __gcd(i,j);
const int N=1e5+5;
const int mod=1e9+7;
const double eps=1e-8;

int n;
struct NODE { int x,t; }a[N];
bool cmp(NODE p,NODE q) { return p.x<q.x; }
int last[N<<1];

int main()
{
    while(~scanf("%lld",&n)) {
        inc(i,1,n) {
            scanf("%d",&a[i].x);
            char c; scanf(" %c",&c);
            if(c==‘G‘) a[i].t=1;
            else a[i].t=-1;
        }
        sort(a+1,a+1+n,cmp);
        mem(last,0); last[N]=a[1].x;
        int sum=N, ans=0;
        inc(i,1,n) {
            sum+=a[i].t; int t=ans;
            if(last[sum]==0) last[sum]=a[i+1].x;
            else ans=max(ans,a[i].x-last[sum]);
        }
        inc(i,1,n) {
            int j=i;
            while(j<=n && a[j].t==a[i].t) j++;
            j--; ans=max(ans,a[j].x-a[i].x);
            i=j;
        } // 只包含一个品种的情况
        printf("%d\n",ans);
    }

    return 0;
}