向量C ++按字母顺序排列的快速排序

Question

For the following code I've been trying to implement Quicksort to Alphabetically Sort a Vector of strings.

The issue I have found is that you cannot compare strings as ">" or "<". I've also attempted using the .compare function for strings.

Any Advice?

`void quicksort(vector<string> arr, int left, int right)
 {
  int i = left, j = right;
  string tmp;
  string pivot = arr[(left + right) / 2];

  /* partition */
  while (i <= j) {
        while (arr[i] < pivot)
              i++;
        while (arr[j] > pivot)
              j--;
        if (i <= j) {
              tmp = arr[i];
              arr[i] = arr[j];
              arr[j] = tmp;
              i++;
              j--;
    }
}
/* recursion */
if (left < j)
    quickSort(arr, left, j);
if (i < right)
        quickSort(arr, i, right);
}`

I Will also Later be attempting MergeSort, and InsertSort

Answer 1

The issue I have found is that you cannot compare strings as ">" or "<".

False. std::string provides overloaded < and > that you can use for comparison.

The problem you're having is that you're passing the arr argument by value. You should pass it by reference to be able to modify the original vector you passed to quicksort :

void quicksort(vector<string>& arr, int left, int right)