51.数组中重复的数字.cpp

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;
            while(numbers[i] != i){
                if(numbers[i] == numbers[numbers[i]]){
                    *duplication = numbers[i];
                    return true;
                }
                if(numbers[numbers[i]] < 0 || numbers[numbers[i]] > length - 1)	return false;
                swap(numbers[i], numbers[numbers[i]]);
            }
        }
        return false;
    }
};