[中等]寻找缺失的数

题目来源：http://www.lintcode.com/zh-cn/problem/find-the-missing-number/

C++版 VS2012测试通过：

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

//方法1
class Solution {
public:
    /**    
     * @param nums: a vector of integers
     * @return: an integer
     */
    int findMissing(vector<int> &nums) {
        // write your code here
        int n=nums.size()+1;
        int sum=(n-1)*n/2;
        for(int i=0;i<nums.size();i++)
            sum-=nums[i];
        return sum;
    }
};

//方法2
class Solution {
public:
    /**    
     * @param nums: a vector of integers
     * @return: an integer
     */
    int findMissing(vector<int> &nums) {
        // write your code here
        sort(nums.begin(),nums.end());
        for(long i=0;i<nums.size();i++)
        {
            if(nums[i]!=i)
                return i;
        }
        return nums.size();
    }
};

int main () 
{
    int a[5]={0,1,2,3,5};
    vector<int> v(a,a+5);
    Solution s;
    cout<<s.findMissing(v);
}