题解 | #数组中重复的数字#

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param numbers int整型vector 
     * @return int整型
     */
    int duplicate(vector<int>& numbers) {
        // write code here
        int res = -1;
        for (int i = 0; i < numbers.size(); ++i) {
            while (numbers[i] != i) {
                if (numbers[i] == numbers[numbers[i]]) {
                    return numbers[i];
                }
                int tmp = numbers[i];
                numbers[i] = numbers[tmp];
                numbers[tmp] = tmp;
            }
        }
        return res;
    }
};