福建农大 1084 检查站

单调队列 见 http://www.cnblogs.com/lxf90/articles/2012016.html

第一，原序列的坐标单调

第二，原序列的值单调

/*单调队列 */
#include <stdio.h>
using namespace std;
const int MAXN = 100001;
struct dqueue{
    int val;
    int idx;
}que[MAXN];
int a[MAXN], cnt;
int head, tail;
int lefts;
int main(){
    int n;
    //cin >> n;
    scanf("%d",&n);
    head = tail = 0;
    cnt = 0;
    lefts = 0;
    for(int i = 0; i < n; ++i){
        //string s;
        //cin >> s;
        char s[20];
        scanf("%s",s);
        if(s[0] == 'Q'){
            if( head > tail ){
                //cout << "0" << endl;    
                printf("0\n");
            } else {
                //cout <<que[head].val << endl;    
                printf("%d\n",que[head].val);
            }
        } else if(s[0] == 'I'){
            //cin >> a[cnt++];
            scanf("%d",&a[cnt++]);
            if(head > tail){
                head = tail = 0;
                que[head].idx = cnt - 1;
                que[head].val = a[cnt - 1];
                continue;    
            }
            while (head <= tail && que[tail].val <= a[cnt - 1])    
                tail--;
            ++tail;
            que[tail].val = a[cnt - 1];
            que[tail].idx = cnt - 1;
        } else {
            lefts++;
            if(que[head].idx < lefts)
                head++;                    
        }
    }
    return 0;
}