1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
#include <bits/stdc++.h>
#include <iostream>
using namespace std;

constexpr int M = 1e9+7, N=3e5+10;

int magic(int x)
{
    return x & (-x);
}

class Tree 
{
public:
    Tree(size_t size) : size(size)
    {
        values.assign(size+1, 0);
    }

    void update(int x, int val)
    {
        while(x <= size)
        {
            values[x] += val;
            values[x] %= M;
            x += magic(x);
        }
    }

    int collect(int x)
    {
        int res = 0;

        while(x != 0)
        {
            res += values[x];
            res %= M;
            x -= magic(x);
        }
        return res;
    }

    int collect_range(int a, int b)
    {
        return (collect(b) - collect(a-1) + M) % M;
    }

    int collect_upper(int a)
    {
        return collect_range(a, size);
    }

private:
    size_t size;
    vector<int> values;
};


void remove_duplicates(vector<int> &vec)
{
    sort(vec.begin(), vec.end());
    vec.erase(unique(vec.begin(), vec.end()), vec.end());
}

int main()
{
    ios_base::sync_with_stdio(false);
    int pref=0;
    int n;
    cin >> n;

    vector<int> values, parz, nparz;

    for(int i=0; i < n; i++)
    {
        int a;
        cin >> a;
        pref += a;
        pref %= M;
        values.push_back(pref);
        if (pref % 2 == 0) {
            parz.push_back(pref);
        }
        else {
            nparz.push_back(pref);
        }
    }


    remove_duplicates(parz);
    remove_duplicates(nparz);

    Tree nparzTree(nparz.size()), parzTree(parz.size());
    
    for (int i=0; i < n; i++)
    {
        int res;
        if (values[i] % 2 == 0) {
            res = 1;

            int idx = distance(parz.begin(), lower_bound(parz.begin(), parz.end(), values[i])) + 1;

            res += parzTree.collect(idx);

            res %= M;

            auto it = lower_bound(nparz.begin(), nparz.end(), values[i]);
            if (it != nparz.end()) {
                int idy = distance(nparz.begin(), it) + 1;
                res += nparzTree.collect_upper(idy);
                res %= M;
            }

            parzTree.update(idx, res);
        }
        else {
            res = 0;

            int idx = distance(nparz.begin(), lower_bound(nparz.begin(), nparz.end(), values[i])) + 1;

            res += nparzTree.collect(idx);

            res %= M;

            auto it = lower_bound(parz.begin(), parz.end(), values[i]);
            if (it != parz.end()) {
                int idy = distance(parz.begin(), it) + 1;
                res += parzTree.collect_upper(idy);
                res %= M;
            }

            nparzTree.update(idx, res);
        }

        if (i == n-1) {
            cout << res;
        }
    }
}