Codeforces 492C Vanya and Exams(贪心)

题目链接：Codeforces 492C Vanya and Exams

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long ll;const int maxn = 1e5 + 5;struct Exams {int a, b;}ex[maxn];int N, R, avg;ll S;inline bool cmp (const Exams& A, const Exams& B) {return A.b < B.b;}void init () {S = 0;scanf("%d%d%d", &N, &R, &avg);for (int i = 0; i < N; i++) {scanf("%d%d", &ex[i].a, &ex[i].b);S += ex[i].a;}sort(ex, ex + N, cmp);}int main () {init();ll ans = 0, T = 1LL * N * avg;for (int i = 0; i < N; i++) {if (S >= T)break;ll add = min((ll)R - ex[i].a, T - S);ans += add * ex[i].b;S += add;}printf("%lld\n", ans);return 0;}