为何稳定匹配问题是O(n^2)的？

#include<bits/stdc++.h>
const int N=1010;
int n,a[N][N],b[N][N],f[N],g[N];
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        for(int j=1;j<=n;++j)
            scanf("%d",&a[i][j]);
    for(int i=1;i<=n;++i)
        for(int x,j=1;j<=n;++j){
            scanf("%d",&x);
            b[i][x]=n-j+1;
        }
    while(std::all_of(f+1,f+n+1,[](int x){return x;}))
        for(int i=1,j;i<=n;++i)if(!f[i]){
            j=a[i][++a[i][0]];
            if(b[j][i]>b[j][g[j]]){
                f[g[j]]=0;
                f[i]=j;
                g[j]=i;
            }
        }
    for(int i=1;i<=n;++i)
        printf("%d\n",g[i]);
}