| 非正经题解 | 删除元素使数组去重

#include<iostream>
#include<vector>
#include<unordered_set>
using namespace std;
bool op1(const vector<int>& arr) {
    unordered_set<int>seen;
    for (int num:arr) {
        if (seen.find(num)!=seen.end()) {
            return true;
        }
        seen.insert(num);
    }
    return false;
}
int op2(const vector<int>&arr) {
    int n=arr.size();
    for (int i=0;i<n;++i) {
        vector<int>subArr(arr.begin()+i,arr.end());
        if (!op1(subArr)) {
            return i;
        }
    }
    return -1;
}
int main(){
    int N;
    cin>>N;
    vector<int>A(N);
    for (int i=0;i<N;++i) {
        cin>>A[i];
    }
    int result =op2(A);
    cout<<result<<endl;
    return 0;
}