和为S的连续正数序列

class Solution {
public:
    vector<vector<int> > FindContinuousSequence(int sum) {
        vector<vector<int>> allRes;
        int phigh=2,plow=1;
        
        while(phigh > plow) {
            int cur=(phigh +plow)*(phigh-plow +1)/2;
            if(cur<sum)
                phigh++;
            
            if(cur==sum){
                vector<int> res;
                for(int i=plow;i<=phigh;i++)
                    res.push_back(i);
                allRes.push_back(res);
                plow++;
            }
            
            if(cur>sum)
                plow++;
        }
        return allRes;
    }
};

typedef vector<int> vi;
typedef vector<vi> vvi;
class Solution {
public:
    vvi FindContinuousSequence(int sum) {
        vvi res;
        sum <<= 1;
        for(int i = 2; i * i <= sum; ++i) if(sum % i == 0){
            int j = sum / i, t = (j - i + 1);
            if(!(t & 1)){
                res.push_back(vi());
                vi& v = res[res.size() - 1];
                t >>= 1;
                for(int a = t; a <= j - t; ++a) v.push_back(a);
            }
        }
        for(int i = 0, j = int(res.size()) - 1; i < j; ++i, --j) swap(res[i], res[j]);
        return res;
    }
};