老哥们,请问我做的对么?(记一次失败的st表乱搞)

今天a开始就不是很顺,然后到d,d努力读完题理解完题意,感觉自己又行了{

问最大的jump,我觉得如果单纯贪心策略显然会t,问min,max这类rmq果断上了st表(这东西我隔离的时候写的,没想到被拉出来用上了)。然后冥思苦想怎么才能满足跳的条件。

突然一个大胆的想法从脑中诞生,二分吧,自己动手模拟了下,感觉st表满足单调性的性质,毕竟min和max是区间内,只有扩大和缩小区间才能对其产生影响,而这种影响应该是符合单调性(然而没想到的一点是少考虑了一些问题)。然后复杂度一计算,nlogn刚好可以过!

怀着激动的心情码了出来,提交然后wa5,一直到最后也没调出来,我吐了,后来发现正解是单调栈,但二分st表并非不行(应该多一步就对了,去重是可以O(1)得到的

哎还是记录一下吧,好好练习,专心刷题,不要三心二意呢

#include <bits/stdc++.h>
using namespace std;
#define limit (500000 + 5)//防止溢出
#define INF 0x3f3f3f3f
#define inf 0x3f3f3f3f3f
#define lowbit(i) i&(-i)//一步两步
#define EPS 1e-6
#define FASTIO  ios::sync_with_stdio(false);cin.tie(0);
#define ff(a) printf("%d\n",a );
#define pi(a,b) pair<a,b>
#define rep(i, a, b) for(ll i = a; i <= b ; ++i)
#define per(i, a, b) for(ll i = b ; i >= a  ; --i)
#define MOD 998244353
#define traverse(u) for(int i = head[u]; ~i ; i = edge[i].next)
#define FOPEN freopen("C:\\Users\\tiany\\CLionProjects\\acm_01\\data.txt", "rt", stdin)
#define FOUT freopen("C:\\Users\\tiany\\CLionProjects\\acm_01\\dabiao.txt", "wt", stdout)
#define debug(x) cout<<x<<endl
typedef long long ll;
typedef unsigned long long ull;
inline ll read(){
    ll sign = 1, x = 0;char s = getchar();
    while(s > '9' || s < '0' ){if(s == '-')sign = -1;s = getchar();}
    while(s >= '0' && s <= '9'){x = (x << 3) + (x << 1) + s - '0';s = getchar();}
    return x * sign;
}//快读
void write(ll x){
    if(x < 0) putchar('-'),x = -x;
    if(x / 10) write(x / 10);
    putchar(x % 10 + '0');
}

int n,m;
int kase;
int a[limit];

int f[limit][1<<6] , g[limit][1<<6];

void build(){
    rep(i , 1, n){
        f[i][0] = g[i][0] = a[i];
    }
    for(int j = 1; (1<<j) <= n; ++j){
        for(int i = 1; i + (1<<j) - 1 <= n; ++i){
            f[i][j] = max(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
            g[i][j] = min(g[i][j - 1], g[i + (1 << (j - 1))][j - 1]);
        }
    }
}
int query(int l, int r){
    int tmp = log2(r - l + 1);
    return min(g[l][tmp] , g[r - (1 << tmp) + 1][tmp]);
}
int querymax(int l, int r){
    int tmp = log2(r - l + 1);
    return max(f[l][tmp] , f[r - (1 << tmp) + 1][tmp]);
}
bool judge(int st, int x){//开始和x
    bool flag = querymax(st + 1, st + x) < min({a[st], a[st + x + 1]});
    bool flag2 = query(st + 1, st + x) > max(a[st], a[st + x + 1]);
    return flag || flag2;
}
int check(int st){
    int l = 1, r = n - st;
    int mid;
    while (l <= r){
        mid = l + (r - l) / 2;
        if(judge(st,mid))l = mid + 1;
        else r = mid - 1;
    }
    return l + (r - l) / 2;
}
int main() {
#ifdef LOCAL
    FOPEN;
#endif
    cin>>n;
    rep(i ,1,n){
        a[i] = read();
    }
    build();
    ll ans = 0;
    for(int i = 1 ; i < n ; i += check(i),++ans);
    cout<<ans<<endl;
    return 0;
}

 

posted @ 2020-09-09 01:26  tiany7  阅读(185)  评论(0编辑  收藏  举报