Missing Coin Sum
Key Idea: Sort the coins and greedily extend the reachable prefix sum, stopping at the first gap.
Solution
#include <bits/stdc++.h>
using namespace std;
//author: von_Braun
#define ll long long
#define lli long long int
#define pb push_back
#define rep(var, start, num) for(ulli var = start; var <start + num; var++)
#define all(x) x.begin(), x.end()
#define ulli unsigned long long int
#define ull unsigned long long
bool sortbysec(const pair<ll,ll> &a,const pair<ll,ll> &b) { return (a.second < b.second); }
void solve() {
int n;
cin>>n;
int a[n];
rep(i,0,n) {cin>>a[i];}
sort(a,a+n);
ll s=0;
bool fl=0;
rep(i,0,n) {
if (a[i]>s+1) {
cout<<s+1<<endl;
fl=1;
break;
} else {
s+=a[i];
}
}
if (!fl) {cout<<s+1<<endl;}
}
int main() {
//add quotes incase input output file
//freopen(input.txt,r,stdin);
//freopen(output.txt,w,stdout);
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
for (int t = 1; t <= tc; t++) {
solve();
}
}