晕，手写了一个冒泡，为什么错了啊

#include <bits/stdc++.h>
using namespace std;
int n,ans,a[100001],b[100001];
int main(){
    scanf ("%d",&n);
    for (int i=0;i<n;i++)scanf ("%d",&a[i]),b[i]=a[i];
    sort(a,a+n);
    for (int i=0;i<n;i++)
    if (b[i]!=a[i])ans++,a[i]^=b[i]^=a[i]^=b[i];
    printf ("%d",ans);
}