CF1334C Circle of Monsters（贪心）

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<map>
#include<string>
#include<vector>
using namespace std;
typedef long long ll;
const int N=1e6+10;
ll a[N],b[N],s[N];
ll res[N];
int main(){
    int t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        int i;
        for(i=1;i<=n;i++){
            scanf("%lld%lld",&a[i],&b[i]);
        }
        ll sum=0;
        for(i=1;i<=n;i++){
            if(i==1){
                res[i]=a[i]-b[n];
            }
            else{
                res[i]=a[i]-b[i-1];
            }
            if(res[i]>0)
                sum+=res[i];
        }
        ll ans=1e18;
        for(i=1;i<=n;i++){
            ans=min(ans,sum-max(res[i],0ll)+a[i]);
        }
        cout<<ans<<endl;
    }
    return 0;
}