BZOJ 1113 海报 单调栈

题目链接：

https://www.lydsy.com/JudgeOnline/problem.php?id=1113

题目大意：

N个矩形,排成一排. 现在希望用尽量少的矩形海报Cover住它们.

思路：

直接维护一个递增的单调栈，注意如果栈顶元素和当前值相同，那么当前值不加入栈中。

#include<bits/stdc++.h>
#define IOS ios::sync_with_stdio(false);//不可再使用scanf printf
#define Max(a, b) ((a) > (b) ? (a) : (b))//禁用于函数，会超时
#define Min(a, b) ((a) < (b) ? (a) : (b))
#define Mem(a) memset(a, 0, sizeof(a))
#define Dis(x, y, x1, y1) ((x - x1) * (x - x1) + (y - y1) * (y - y1))
#define MID(l, r) ((l) + ((r) - (l)) / 2)
#define lson ((o)<<1)
#define rson ((o)<<1|1)
#define Accepted 0
#pragma comment(linker, "/STACK:102400000,102400000")//栈外挂
using namespace std;
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
    while (ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
typedef long long ll;
const int maxn = 1000000 + 10;
const int MOD = 1000000007;//const引用更快，宏定义也更快
const int INF = 1e9 + 7;
const double eps = 1e-6;

stack<int>q;
int main()
{
    int n, ans = 0, x, y;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
    {
        scanf("%d%d", &x, &y);
        while(!q.empty() && q.top() > y)
        {
            q.pop();
            ans++;
        }
        if(!q.empty() && q.top() == y)continue;
        q.push(y);
    }
    ans += q.size();
    printf("%d
", ans);
    return Accepted;
}