具体看    这里

题目就是要让两个序列都递增。

那么放入数组之后   下标递增的同时  值也递增

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

int save[500005];
int len_min[500005];
int n;
int bin(int l,int r,int key)
{
    int mid;
    while(l<r)
    {
        mid=(l+r)>>1;
        if(len_min[mid]<key)l=mid+1;
        else r=mid;
    }
    return l;
}
int LIS()
{
    int top=1;
    len_min[0]=save[1];
    for(int i=2;i<=n;i++)
    {
        int k=bin(0,top-1,save[i]);
        if(len_min[k]>=save[i])len_min[k]=save[i];
        else len_min[top++]=save[i];
    }
    return top;
}
int main()
{
    int kase=1;
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1;i<=n;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            save[x]=y;
        }
        int ans=LIS();
        printf("Case %d:\n",kase++);
        if(ans==1)printf("My king, at most 1 road can be built.\n\n");
        else printf("My king, at most %d roads can be built.\n\n",ans);
    }
    return 0;
}

hdu 1025 Constructing Roads In JGShining's Kingdom （O(nlogn) 求LIC）