Shortest Distance (20)

规律：，发现①环形的总长度是可求的②A到B之间的距离等于（A到0距离）减去（B到0距离）③任意节点到0的距离都可以在输入时求出。

#include<bits/stdc++.h>
using namespace std;
#define ll long long
const double pi=acos(-1.0);
const double eps=1e-8;
const int maxn=100005;
int a[maxn];
ll sum[maxn];
ll  maxx;
int main()
{
    int n;
    scanf("%d",&n);
    maxx=0;
    for(int i=1; i<=n; i++)
    {
        scanf("%d",&a[i]);
        sum[i]=sum[i-1]+a[i];
        maxx+=a[i];
    }
    int m;
    scanf("%d",&m);
    while(m--)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        ll ans=0;
        if(x<y)
        {
            ll ans1=0;
            ll ans2=0;
            ans1=sum[y-1]-sum[x-1];
            ans2=sum[x-1]+maxx-sum[y-1];
            ans=min(ans1,ans2);
        }
        else
        {
            ll ans1=0;
            ll ans2=0;
            ans1=sum[y-1]+maxx-sum[x-1];
            ans2=sum[x-1]-sum[y-1];
            ans=min(ans1,ans2);
        }
        printf("%lld\n",ans);
    }
}