PKU 2531 Network saboteur (dfs+ pruning | | randomization algorithm)

Title: Link to original topic

Given n nodes, the right value between any two nodes, divide the n nodes into a A, a, two set, so that each node in the a set is combined with each node 22 in the B set (that is, there is | a|*| b| ) The sum of the weights is the largest.

Tag: A set: True B Set: false

Solution One: dfs+ pruning

#include <iostream>#include<cstring>using namespacestd;intN,ans;BOOL inch[ -];intgraph[ -][ -];voidDfsintIintcursum) {    inch[i]=true; intmaxsum=cursum;  for(intj=1; j<=n;j++){        if(!inch[j]) maxsum+=Graph[i][j]; Elsemaxsum-=Graph[i][j]; }    if(Maxsum>ans) ans=maxsum; if(maxsum>cursum) {//Enumeration + recursion         for(intj=i+1; j<=n;j++) DFS (j,maxsum); }//if the addition of Group A does not cause the maxsum to increase, it does not add in    inch[i]=false; }intMain () {CIN>>N; memset (inch,0,sizeof(inch));  for(intI=1; i<=n;i++){         for(intj=1; j<=n;j++) Cin>>Graph[i][j]; } ans=0; DFS (1,0); cout<<ans<<Endl;}

Solution Two: randomization algorithm (good magic Idea)

#include <iostream>#include<cstdlib>using namespacestd; Const inttle= -;//time limit is 2000msintMain () {intn,m[ -][ -]; CIN>>N;  for(intI=1; i<=n;i++){         for(intj=1; j<=n;j++) Cin>>M[i][j]; }    /*Random Algorithm*/      BOOL inch[ -]={false}; intTime= -*tle;//make random times as large as possible, random results as close as possible to optimal solutions    intmaxsum=0, cursum=0;  while(time--){          intX=rand ()%n+1;//Range: 1~n        inch[x]=!inch[x];//change the collection position where x is located         for(intI=1; i<=n;i++){            if(inch[i]!=inch[x]) cursum+=M[i][x]; Elsecursum-=M[i][x]; }        if(maxsum<cursum) maxsum=cursum; } cout<<maxsum<<Endl;}

PKU 2531 Network saboteur (dfs+ pruning | | randomization algorithm)