51Nod 1272 最大距离 (栈或贪心)

#include <cstdio>
#include <queue>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <stack>
using namespace std;

typedef long long ll;
struct node{int v, id;};
stack<node>q, sq;

int main(){
    int n;
    scanf("%d", &n);
    while(!sq.empty())  sq.pop();
    int ans = 0;
    for(int i = 0;i < n;i++){
        int x;
        scanf("%d", &x);
        node a;
        a.v = x; a.id = i;
        if(sq.size() == 0 || sq.top().v > x){
            sq.push(a);
        }
        else{
            while(sq.top().v <= x){
                ans = max(ans, i - sq.top().id);
                q.push(sq.top());
                sq.pop();
                if(sq.empty())
                    break;
            }
            while(!q.empty()){
                sq.push(q.top());
                q.pop();
            }
        }
    }
    printf("%d
", ans);
    return 0;
}

 后来提交一波的时候，最后一组数据超时，于是改用贪心，排序一遍过的：

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn = 50000+5;
struct node{
    int id,v;
}a[maxn];

bool cmp(node xx,node yy)
{
    if (xx.v!=yy.v)
    return xx.v<yy.v;
    return xx.id<yy.id;
}

int main()
{
    int n;
    scanf("%d",&n);
    for (int i=0;i<n;i++)
    {
        scanf("%d", &a[i].v);
        a[i].id=i;
    }
    sort(a,a+n,cmp);
    int ans = 0,Min=a[0].id;
    for (int i=1;i<n;i++)
    {
        if (a[i].id > Min)
            ans = max(ans, a[i].id-Min);
        else Min = a[i].id;
    }
    printf("%d
",ans);
    return 0;
}