C++ c++；如何使用for循环查找重复项 #包括 #包括 使用名称空间std； int*randnum（int*arr，int n）{ int*ar=新的int[n/2]； 对于（int i=0；i

问题在这里：

#include <iostream>
#include <vector>
using namespace std;


int* randnum(int* arr, int n) {
    int *ar = new int[n / 2];

    for (int i = 0; i < n/2; i++) {
        ar[i] = rand() % n + 1;
    }

    return ar;
}

bool duplication(int* ar, int size) {

    if (size <= 1) {
        return false;
    }

    for (int i = 0; i <= size; i++) {
        for (int j = i+1; j <= size; j++) {

            if (ar[i] == ar[j]) {
                return true;
            }

            else
                return false;
        }
    }

}

int main() {
    int n;
    while (true) {
        cout << "Please enter a number : ";
        cin >> n;

        int size = n / 2;

        if (n <= 2) {
            cout << "Wrong number!!!" << endl;
            break;
        }

        cout << "Size of random array : " << size << endl;

        int* arr = new int[size];

        cout << endl;
        cout << "[ Array ]" << endl;

        arr = randnum(arr, n);

        cout << endl;

        for (int i = 0; i < size; i++) {
            cout << arr[i] << "\t";
        }
        cout << endl;

        cout << endl;

        if (duplication(arr,size) == true)
            cout << "Duplicates found." << endl;

        if (duplication(arr, size) == false)
            cout << "Duplication not found." << endl;

        cout << endl;
        cout << "-----------------------------------------------------------";
        cout << endl;
    }


    system("pause");
    return 0;
}

---

天哪！太感谢你了：）我花了很多时间来解决这个问题，太感谢你了第二个问题（第一个问题被掩盖了）：外环从数组的末端运行。

i@PeteBecker你说得对，我改变了建议，改为使用
std:：nexture\u find
。
for (int i = 0; i <= size; i++) {
        for (int j = i+1; j <= size; j++) {

            if (ar[i] == ar[j]) {
                return true;
            }

            else
                return false;
        }
    }

bool duplication(int* ar, int size) {
    return (std::adjacent_find(ar, ar + size) != ar + size);
}