LeetCode 209. 长度最小的子数组

LeetCode 209. 长度最小的子数组

前缀和 + 二分

class Solution {
    
public:
    int minSubArrayLen(int target, vector<int>& nums) {
    
        int n = nums.size();
        int s[n + 1] = {
    0};
        for(int i = 1; i <= n; i ++) s[i] = s[i - 1] + nums[i - 1];
        
        int res = 1e9;
        for(int i = 1; i <= n; i ++)
        {
    
            int t = s[i] - target;
            int l = 0, r = n;
            while(l < r)
            {
    
                int mid = (l + r + 1) >> 1;
                if(s[mid] <= t) l = mid;
                else r = mid - 1;
            }
            if(s[r] <= t) res = min(res, i - r);
        }
        return res == 1e9 ? 0 : res;
    }
};

滑动窗口 / 双指针

class Solution {
    
public:
    int minSubArrayLen(int target, vector<int>& nums) {
    
        int sum = 0, res = 1e9;
        for(int l = 0, r = 0; r < nums.size(); r ++)
        {
    
            sum += nums[r];
            while(sum >= target)
            {
    
                res = min(res, r - l + 1);
                sum -= nums[l ++];
            }
        }
        return res == 1e9 ? 0 : res;
    }
};