hdoj1025 Constructing Roads In JGShining's Kingdom(DP+二分法)

第一次提交超时了。

借鉴了一下别人的代码，发现dp的思路都错了。。。

而且还得用到二分法来减小时间复杂度。

dp+二分法。好题呀。

#include<iostream>using namespace std;int p[500005],dp[500005]; int search(int num,int low,int high){    int mid;    while (low <= high)    {        mid = (low + high) / 2;        if (num >= dp[mid]) low = mid + 1;        else high = mid - 1;    }    return low;}int main(){int len,pos,k=1;int n,i,a,b,max;while(cin>>n){max=0;len=1;memset(p,0,n+5);memset(dp,0,n+5);for( i=1;i<=n;i++){cin>>a>>b;p[a]=b;}dp[1]=p[1];for(i=2;i<=n;i++){if(p[i]>dp[len]){dp[++len]=p[i];}else{pos=search(p[i],1,len);dp[pos]=p[i];}}if(len==1)cout<<"Case "<<k<<":"<<endl<<"My king, at most 1 road can be built."<<endl;else   cout<<"Case "<<k<<":"<<endl<<"My king, at most "<<len<<" road can be built."<<endl;k++;}return 0;}