学步园

做这题算是张见识了，随机化算法，随机啊！！！坑爹呢有木有？

code：

#include <set>
#include <map>
#include <ctime>
#include <queue>
#include <cmath>
#include <stack>
#include <limits>
#include <vector>
#include <bitset>
#include <string>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <string.h>
#include <iostream>
#include <algorithm>
#define ls rt<<1
#define rs rt<<1|1
#define Si set<int>
#define LL long long
#define pb push_back
#define PS printf(" ")
#define Vi vector<int>
#define LN printf("\n")
#define SD(a) scanf("%d",&a)
#define PD(a) printf("%d",a)
#define SET(a,b) memset(a,b,sizeof(a))
#define FF(i,a) for(int i(0);i<(a);i++)
#define FD(i,a) for(int i(a);i>=(1);i--)
#define FOR(i,a,b) for(int i(a);i<=(b);i++)
#define FOD(i,a,b) for(int i(a);i>=(b);i--)
#define readf freopen("input.txt","r",stdin)
#define writef freopen("output.txt","w",stdout)
const int maxn = 21;
const int INF = 0x3fffffff;
const int BigP = 99991;
const int dx[] = {0,1,0,-1};
const int dy[] = {1,0,-1,0};
const double pi = acos(-1.0);
using namespace std;
int N,w[maxn][maxn];
bool subset[maxn];
int main(){
    SD(N);
    FOR(i,1,N) FOR(j,1,N) SD(w[i][j]);
    int sum=0,maxx=0;
    int times=100000;
    while(times--){
        int x=rand()%N+1;
        subset[x]=!subset[x];
        FOR(i,1,N){
            if(subset[i]!=subset[x]) sum+=w[i][x];
            if(i!=x && subset[i]==subset[x]) sum-=w[i][x];
        }
        maxx=max(sum,maxx);
    }
    PD(maxx);LN;
	return 0;
}