A[i] < A[j] && i < j, then A[i] has a surpasser A[j], calc the max surpasser inside an array

surpasser.cpp

#include <iostream>
#include <string>
#include <vector>
#include <stack>
#include <sstream>
using namespace std;

struct NumExt {
  int val;
  int index;
  int spCnt;
  NumExt(int _val, int _index, int _cnt): val(_val), index(_index), spCnt(_cnt) {}
};

void mergeSortEx(vector<NumExt> &numext, int left, int right) {
  if (left >= right) {
    return;
  }
  int mid = (left + right) / 2;
  mergeSortEx(numext, left, mid);
  mergeSortEx(numext, mid + 1, right);
  vector<NumExt> tmpArr;
  int lower = left;
  int upper = mid + 1;
  while (lower <= mid && upper <= right) {
    if (numext[lower].val < numext[upper].val) {
      tmpArr.push_back(numext[upper++]);
    } else {
      numext[lower].spCnt += upper - mid - 1;
      tmpArr.push_back(numext[lower++]);
    }
  }
  while (lower <= mid) {
    numext[lower].spCnt += upper - mid - 1;
    tmpArr.push_back(numext[lower++]);
  }
  while (upper <= right) {
    tmpArr.push_back(numext[upper++]);
  }
  for (int i = 0; i < tmpArr.size(); i++) {
    numext[left + i] = tmpArr[i];
  }
}

int maxSupasser(vector<int> &num) {
  vector<NumExt> numext;
  for (int i = 0; i < num.size(); i++) {
    NumExt tmp(num[i], i, 0);
    numext.push_back(tmp);
  }
  mergeSortEx(numext, 0, numext.size() - 1);
  int maxIdx = 0;
  int maxCnt = 0;
  for (int i = 0; i < numext.size(); i++) {
    cout << numext[i].val << ": " << numext[i].spCnt << ", ";
    if (numext[i].spCnt > maxCnt) {
      maxCnt = numext[i].spCnt;
      maxIdx = numext[i].index;
    }
  }
  cout << endl;
  return maxIdx;
}

int main() {
  // int vv[7] = {1, 2, 3, 4, 5, 6, 7};
  // int vv[7] = {7, 6, 5, 4, 3, 2, 1};
  // int vv[7] = {4, 3, 2, 1, 7, 6, 5};
  // int vv[7] = {6, 4, 2, 1, 3, 5, 7};
  int vv[7] = {6, 4, 2, 3, 1, 5, 7};
  vector<int> v(&vv[0], &vv[0] + 7);
  int i = maxSupasser(v);
  cout << v[i] << endl;
  return 0;
}