class Solution { public: // Parameters: // numbers: an array of integers // length: the length of array numbers // duplication: (Output) the duplicated number in the array number // Return value: true if the input is valid, and there are some duplications in the array number // otherwise false bool duplicate(int numbers[], int length, int* duplication) { if (numbers == NULL || length <= 0) return false; for (int i = 0; i < length; ++ i) { if (numbers[i] < 0 || numbers[i] > length-1) return false; } for (int i = 0; i < length; ++ i) { while(numbers[i] != i) { if (numbers[numbers[i]] == numbers[i]) { *duplication = numbers[i]; return true; } swap(numbers[i], numbers[numbers[i]]); } } return false; } };