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  • Eugene and an array CodeForces

    Eugene likes working with arrays. And today he needs your help in solving one challenging task.

    An array cc is a subarray of an array bb if cc can be obtained from bb by deletion of several (possibly, zero or all) elements from the beginning and several (possibly, zero or all) elements from the end.

    Let's call a nonempty array good if for every nonempty subarray of this array, sum of the elements of this subarray is nonzero. For example, array [1,2,3][−1,2,−3] is good, as all arrays [1][−1], [1,2][−1,2], [1,2,3][−1,2,−3], [2][2], [2,3][2,−3], [3][−3] have nonzero sums of elements. However, array [1,2,1,3][−1,2,−1,−3] isn't good, as his subarray [1,2,1][−1,2,−1] has sum of elements equal to 00.

    Help Eugene to calculate the number of nonempty good subarrays of a given array aa.

    Input

    The first line of the input contains a single integer nn (1n2×1051≤n≤2×105)  — the length of array aa.

    The second line of the input contains nn integers a1,a2,,ana1,a2,…,an (109ai109−109≤ai≤109)  — the elements of aa.

    Output

    Output a single integer  — the number of good subarrays of aa.

    Examples

    Input
    3
    1 2 -3
    
    Output
    5
    
    Input
    3
    41 -41 41
    
    Output
    3
    

    Note

    In the first sample, the following subarrays are good: [1][1], [1,2][1,2], [2][2], [2,3][2,−3], [3][−3]. However, the subarray [1,2,3][1,2,−3] isn't good, as its subarray [1,2,3][1,2,−3] has sum of elements equal to 00.

    In the second sample, three subarrays of size 1 are the only good subarrays. At the same time, the subarray [41,41,41][41,−41,41] isn't good, as its subarray [41,41][41,−41] has sum of elements equal to 00.

    #include <bits/stdc++.h>
    #include <iostream>
    #include <cstdio>
    #include <cmath>
    #include<cstring>
    #include <algorithm>
    #include <queue>
    #include<map>
    #include<set>
    #include<vector>
    using namespace std;
    typedef long long ll;
    const int inf = 1e9;
    const int mod = 1000000007;
    const int mx = 5e5+10; //check the limits, dummy
    typedef pair<int, int> pa;
    const double PI = acos(-1);
    ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
    #define swa(a,b) a^=b^=a^=b
    #define re(i,a,b) for(int i=(a),_=(b);i<_;i++)
    #define rb(i,a,b) for(int i=(a),_=(b);i>=_;i--)
    #define clr(a) memset(a, -1, sizeof(a))
    #define lowbit(x) ((x)&(x-1))
    #define mkp make_pai
    void sc(int& x) { scanf("%d", &x); }void sc(int64_t& x) { scanf("%lld", &x); }void sc(double& x) { scanf("%lf", &x); }void sc(char& x) { scanf(" %c", &x); }void sc(char* x) { scanf("%s", x); }
    ll n, m, k,ans=0,t,p,x;
    int a[mx];
    
    int main()
    {
        ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);    
        cin >> n;
        vector<ll>pre(n+1,0);
        re(i, 0, n) {
            cin >> x;
            pre[i + 1] = pre[i] + x;
        }
        int start = 0, end = 0;
        set<ll>s= { 0 };
        while (start<n)
        {
            while (end < n && !s.count(pre[end + 1])) {
                ++end;
                s.insert(pre[end]);
            }
            ans += end - start;
            s.erase(pre[start]);
            ++start;
        }
        cout << ans << endl;
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/xxxsans/p/12768082.html
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