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Cod sursa(job #873876)
#include <fstream>
#include <iostream>
using namespace std;
const int MAX_N = 500100;
int v[MAX_N];
int N;
int merge_sort(int, int);
int main() {
ifstream fin("algsort.in");
ofstream fout("algsort.out");
fin >> N;
for (int i = 1; i <= N; ++i) {
fin >> v[i];
}
merge_sort(1, N);
for (int i = 1; i <= N; ++i) {
fout << v[i] << ' ';
}
return 0;
}
int merge_sort(int lo, int hi) {
if (lo == hi) return 0;
int mid = lo + (hi - lo) / 2, numInv;
numInv = merge_sort(lo, mid) + merge_sort(mid + 1, hi);
int aux[MAX_N];
for (int i = lo, j = mid + 1, k = lo; i <= mid || j <= hi; ++k) {
if ((i <= mid && v[i] < v[j]) || j > hi) {
aux[k] = v[i++];
} else {
aux[k] = v[j++];
numInv += (mid - i + 1);
}
}
for (int k = lo; k <= hi; ++k) {
v[k] = aux[k];
}
return numInv;
}