不就O(n log n)吗

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
int cmp(const void* a, const void* b) {
    return *(int*)a - *(int*)b;
}
int main() {
    int n, k;
    scanf("%d %d", &n, &k);
    int* arr = (int*)malloc(n * sizeof(int));
    for (int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    qsort(arr, n, sizeof(int), cmp);
    int left=0,right=n-1;
    bool found=0;
    while (left < right) {
        int sum = arr[left] + arr[right];
        if(sum==k){
            found=1;
            break;
        }else if(sum < k)left++;
        else right--;
    }
    if(found){
        printf("yes\n");
    }else{
        printf("no\n");
    }
    free(arr);
    return 0;
}