hdu1025（nlon(n)最长上升子序列）

 

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1025

 

大致思路：设置两个a,b数组，a数组存储数据，b数组存储最长不降序序列。此算法关键在于设计二分查找。

 

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <queue>

#include <cstdlib>

#include <vector>

#include <set>

#include <map>

#define LL long long

using namespace std;

int dp[50500],a[50500];

int solve(int n)

{

    int len=1,low,high,mid;

    dp[1]=a[1];

    for(int i=2;i<=n;i++)

    {

        low=1;high=len;

        while(low<=high)

        {

            mid=(low+high)/2;

            if(a[i]>dp[mid])low=mid+1;

            else high=mid-1;

        }

        dp[low]=a[i];

        if(low>len)len=low;

    }

    return len;

}

int main()

{

    int n,x,y,cas=1;

    while(scanf("%d",&n)>0)

    {

        for(int i=1;i<=n;i++)

        {

            scanf("%d%d",&x,&y);

            a[x]=y;

        }

        int ans=solve(n);

        printf("Case %d:\n",cas++);

        if(ans==1)

             printf("My king, at most 1 road can be built.\n");

        else

             printf("My king, at most %d roads can be built.\n",ans);

         printf("\n");

    }

}

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