HDU 4699 Editor （2013多校10,1004题）

Editor

Time Limit: 3000/2000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 118 Accepted Submission(s): 38


[align=left]Problem Description[/align]



[align=left]Sample Input[/align]

8
I 2
I -1
I 1
Q 3
L
D
R
Q 2

[align=left]Sample Output[/align]

2
3

Hint

The following diagram shows the status of sequence after each instruction:



[align=left]Source[/align]
2013 Multi-University Training Contest 10

[align=left]Recommend[/align]
zhuyuanchen520

这题只要用双向链表模拟一下。

查询最大前缀和，相当于维护一个单调队列。

/* ***********************************************
Author        :kuangbin
Created Time  :2013/8/22 13:38:35
File Name     :F:\2013ACM练习\2013多校10\1004.cpp
************************************************ */

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
const int MAXN = 1000010;

int a[MAXN];
int next[MAXN],pre[MAXN],tot;
int NewNode()
{
next[tot] = -1;
pre[tot] = -1;
tot++;
return tot-1;
}
int root;
int sum[MAXN];
vector<int>vec;
int now;
int n;
void init()
{
tot = 0;
root = NewNode();
vec.clear();
n = now = 0;
}

void I(int x)
{
n++;
int t = NewNode();
a[t] = x;
pre[t] = now;
next[t] = next[now];
if(next[now] != -1)pre[next[now]] = t;
next[now] = t;
now = t;
if(n == 1)
{
sum
= x;
vec.push_back(n);
}
else
{
sum
= sum[n-1] + x;
int sz = vec.size();
if(sum
> sum[vec[sz-1]])
vec.push_back(n);
}
}
void D()
{
if(n == 0)return;
int sz = vec.size();
if(vec[sz-1] == n)
vec.pop_back();
n--;
int t = pre[now];
next[t] = next[now];
if(next[now] != -1)pre[next[now]] = t;
now = t;
}
void L()
{
if(n == 0)return;
int sz = vec.size();
if(vec[sz-1] == n)
vec.pop_back();
now = pre[now];
n--;
}
void R()
{
if(next[now] == -1)return;
n++;
now = next[now];
if(n == 1)
{
sum
= a[now];
vec.push_back(n);
}
else
{
int sz = vec.size();
sum
= sum[n-1] + a[now];
if(sum
> sum[vec[sz-1]])
vec.push_back(n);
}
}

int Q(int k)
{
int sz = vec.size();
if(vec[sz-1] <= k)
return sum[vec[sz-1]];
int t = upper_bound(vec.begin(),vec.end(),k) - vec.begin();
return sum[vec[t-1]];
}

int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int M;
int x;
char op[10];
while(scanf("%d",&M) == 1)
{
init();
while(M--)
{
scanf("%s",&op);
if(op[0] == 'I')
{
scanf("%d",&x);
I(x);
}
else if(op[0] == 'D')
D();
else if(op[0] == 'L')
L();
else if(op[0] == 'R')
R();
else
{
scanf("%d",&x);
printf("%d\n",Q(x));
}
}
}
return 0;
}