public class Solution {
public int minSubArrayLen(int s, int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
int sum = 0;
int ans = Integer.MAX_VALUE;
for (int l = 0, r = 0; r < nums.length; r++) {
sum += nums[r];
while (sum >= s) {
ans = Math.min(ans, r - l + 1);
sum -= nums[l++];
}
}
return ans == Integer.MAX_VALUE ? 0 : ans;
}
}
This problem is solved by using the two pointers l and r. In the for loop, we incrementally add the element at r to sum. Whenever the sum is greater or equal to s, we calculate the distance between the two pointers (r - l + 1) and if the distance is smaller than ans, we update ans with the distance. Then subtract the element at l from sum and increment l. At the end of the for loop, we should get the length of minimum subarray.
Time Complexity: O(n)
Extra Space: O(1)
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