BZOJ3714: [PA2014]Kuglarz

用s[i]代表1~i的球数，每次查i~j相当于知道了s[j]-s[i-1]的奇偶性
要确切知道每个位置有没有球，就是要知道所有s[i]-s[i-1]的奇偶性
然后对应一个MST的模型= =

code：

#include<set>#include<map>#include<deque>#include<queue>#include<stack>#include<cmath>#include<ctime>#include<bitset>#include<string>#include<vector>#include<cstdio>#include<cstdlib>#include<cstring>#include<climits>#include<complex>#include<iostream>#include<algorithm>#define ll long longusing namespace std;const int maxn = 2100;int n;struct edge{int x,y,c;}a[maxn*maxn]; int len;inline bool cmp(const edge x,const edge y){return x.c<y.c;}int fa[maxn];int findfa(const int x){return fa[x]==x?x:fa[x]=findfa(fa[x]);}ll re;int main(){    scanf("%d",&n);    for(int i=1;i<=n;i++) fa[i]=i;    for(int i=1;i<=n;i++)     {        for(int j=i;j<=n;j++)        {            int x; scanf("%d",&x);            a[++len]=(edge){i-1,j,x};        }    }    sort(a+1,a+len+1,cmp);    for(int i=1;i<=len;i++)    {        int x=a[i].x,y=a[i].y;        int f1=findfa(x),f2=findfa(y);        if(f1!=f2) fa[f2]=f1,re+=a[i].c;    }    printf("%lld\n",re);    return 0;}