Minimum Cost - HackerRank - woman codesprint#2 - study C++ set class

MinimumCost_studyCode_set2.cpp

#include <bits/stdc++.h>

using namespace std;

#define vec vector
#define ALL(x) (x).begin(), (x).end()
#define mp make_pair
#define mt make_tuple

typedef pair< int, int > pii;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

int const inf = 1000 * 1000 * 1000;
ll const inf64 = 1ll * inf * inf;

int const N = 200005;

int n;
ll a[N];

int main() {

    scanf("%d", &n);

    for(int i = 0;i < n;i++) {
        scanf("%lld", &a[i]);
    }

    set< ll > q;
    set< ll > ::iterator fnd;

    ll res = inf64;

    for(int i = n - 1;i >= 0;i--) {
        fnd = q.lower_bound(a[i]);
        if(fnd != q.begin()) {
            fnd--;
            res = min(res, a[i] - *fnd);
        }
        q.insert(a[i]);
    }

    printf("%lld\n", res);

    return 0;
}