bzoj1510: [POI2006]Kra-The Disks(单调栈)

这道题可以O(n)解决，用二分还更慢一点

维护一个单调栈，模拟掉盘子的过程就行了

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
const int maxn = 300010;
int n,m,h[maxn],st[maxn],top,x,now;
int main(){
    scanf("%d%d", &n, &m);
    top=0; h[0]=2000000000;
    for (int i=1; i<=n; i++){
        scanf("%d", &h[i]);
        h[i]=min(h[i],h[i-1]);
        st[++top]=i;
    }
    now=n+1;
    for (int i=1; i<=m; i++){
        scanf("%d", &x);
        while (top && (st[top]>=now || h[st[top]]<x)) top--;
        now=st[top];
    }
    printf("%d
", now);
    return 0;
}