双指针

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
//维护一个动态窗口；
void Print(vector<int>& nums,int k) {

    if(nums.size() == 0 || k <= 0){
        cout << 0 << endl;
        return;
    }

    //定义左右边界
    int left = 0;
    int right = 0;
    int sum = nums[left];
    int len = 0;
    while (left <= right ) {

        if (sum == k) {
            len = max(len,right - left + 1);
            sum -= nums[left++];
        }
        else if (sum < k) {
            right++;
            if (right == nums.size()) {
                break;
            }
            sum += nums[right];
        }
        else {
            sum -= nums[left++];
        }
    }
    cout << len << endl;
}

int main() {

    int n, k;
    while (cin >> n >> k) {
        vector<int> nums(n);
        for (int i = 0; i < n; ++i) {
            cin >> nums[i];
        }
        Print(nums,k);
    }
    return 0;
}