二分解法

#include <bits/stdc++.h>
using namespace std;
vector<int> sum;
struct node
{
    int x, y;
};
vector<node> ans1, ans2;
int minans = 1000000;
int main()
{
    int n, m;
    cin >> n >> m;
    sum.resize(n + 1);
    for(int i = 1; i <= n; i++)
    {
        cin >> sum[i];
        sum[i] += sum[i - 1];
    }
    for(int i = 1; i <= n; i++)
    {
        int l = 1, r = n, mid;
        while(l < r)
        {
            mid = l + (r - l >> 1);
            if(sum[mid] - sum[i - 1] >= m)
                r = mid;
            else
                l = mid + 1;
        }
        if(sum[l] - sum[i-1] == m)
            ans1.push_back({i, l});
        else if(sum[l] - sum[i-1] > m)
        {
            if(sum[l] - sum[i-1] <= minans)
            {
                if(sum[l] - sum[i-1] < minans)
                {
                    minans = sum[l] - sum[i-1];
                    ans2.clear();
                }
                ans2.push_back({i,l});
            }
        }
    }
    if(!ans1.empty())
        for(int i = 0; i < ans1.size(); i++)
            cout << ans1[i].x << "-" << ans1[i].y << endl;
    else
        for(int i = 0; i < ans2.size(); i++)
            cout << ans2[i].x << "-" << ans2[i].y << endl;
    return 0;
}