1025-Wooden Sticks

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经典的最长上升子序列：O（m*m） ---> O(m*logm)

#include<iostream>  #include<algorithm>using namespace std;  int cases;struct Node{int L,W;bool operator<(const Node &node) const{if(L!=node.L)return (L<node.L);elsereturn (W<node.W);}};Node nodes[5001];int res[5001];int n;int maxnum;void TheLongestDec(){int i,j;for(i=1;i<n;i++){for(j=0;j<i;j++){if(nodes[j].W>nodes[i].W && res[j]+1>res[i]){res[i]=res[j]+1;if(res[i]>maxnum)maxnum=res[i];}}}}int main(){cin>>cases;for(int now=1;now<=cases;now++){cin>>n;int i;maxnum=1;for(i=0;i<n;i++){cin>>nodes[i].L>>nodes[i].W;}sort(nodes,nodes+n);fill(res,res+n,1);TheLongestDec();cout<<maxnum<<endl;//for(i=0;i<n;i++)//{//cout<<nodes[i].L<<" "<<nodes[i].W<<endl;//}}return 0;}

在高效一点，利用二分查找

#include<iostream>  #include<algorithm>using namespace std;  int cases;struct Node{int L,W;bool operator<(const Node &node) const //注意：这里要有const不然提交到zju上会出现编译错误{if(L!=node.L)return (L<node.L);elsereturn (W<node.W);}};Node nodes[5001];int query[5001];int n;int top;void BinarySearch(int key) //query中已经是递减的，主要思想就是在同样长度的字串中尽量让最后一个元素最大{int low=0,high=top;int mid;while(low<=high){mid=(low+high)/2;if(query[mid]>key){low=mid+1;}else if(query[mid]<key){high=mid-1;}else if(query[mid]==key)break;}if(query[mid]>key){if(query[mid+1]<key){if(query[mid+1]==-1)top++;query[mid+1]=key;}}else if(query[mid]<key){query[mid]=key;}}void TheLongestDec(){int i;for(i=0;i<n;i++){BinarySearch(nodes[i].W); //利用二分查找}}int main(){cin>>cases;for(int now=1;now<=cases;now++){cin>>n;int i;for(i=0;i<n;i++){cin>>nodes[i].L>>nodes[i].W;}sort(nodes,nodes+n);top=0;fill(query,query+n,-1);query[0]=100000;TheLongestDec();cout<<top<<endl;}return 0;}