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fairdiv_bsearch.cc
59 lines (53 loc) · 1.59 KB
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fairdiv_bsearch.cc
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#include <cstdio>
#include <vector>
long N;
std::vector<int> A;
// S[i] = a0 + ... + a_{i-1}
std::vector<long> S;
// Υπολογίζουμε το άθροισμα a_i + ... + a_j.
long compute_sum(long i, long j) {
if (j < i) return 0;
return S[j+1] - S[i];
}
int main() {
FILE *fi = fopen("fairdiv.in", "r");
fscanf(fi, "%ld", &N);
A = std::vector<int>(N);
S = std::vector<long>(N+1);
S[0] = 0;
for (long i = 0; i < N; ++i) {
fscanf(fi, "%d", &A[i]);
S[i+1] = S[i] + A[i];
}
fclose(fi);
// Ψάχνουμε την καλύτερη μοιρασιά αν δώσουμε τα στοιχεία
// a_0, ..., a_{iA} στον A.
long opt_A = 0, opt_B = 0, opt_C = 0;
for (long iA = 0; iA < N; ++iA) {
long st = iA;
long en = N - 1;
while (st < en) {
long md = (st + en) / 2;
long sum_B = compute_sum(iA + 1, md);
long sum_C = compute_sum(md + 1, N - 1);
if (sum_B < sum_C) st = md + 1;
else en = md;
}
long iB = st;
// Ελέγχουμε αν η τωρινή λύση είναι η καλύτερη.
long sum_A = compute_sum(0, iA);
long sum_B = compute_sum(iA + 1, iB);
long sum_C = compute_sum(iB + 1, N - 1);
if (sum_A >= sum_B && sum_B >= sum_C) {
if (sum_C > opt_C || (sum_C == opt_C && sum_B >= opt_B)) {
opt_A = sum_A;
opt_B = sum_B;
opt_C = sum_C;
}
}
}
FILE *fo = fopen("fairdiv.out", "w");
fprintf(fo, "%ld %ld %ld\n", opt_A, opt_B, opt_C);
fclose(fo);
return 0;
}