003-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==nullptr) return false;
        // 这种解法的前提是数组中的数字在0~n-1内 
        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[i]==numbers[numbers[i]]){
                    *duplication=numbers[i];
                    return true;
                }
                int temp;
                temp=numbers[i];
                numbers[i]=numbers[temp];
                numbers[temp]=temp;
            }
        }
        
        return false;
    }
};