Question Definition
Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn’t one, return 0 instead.
For example, given the array [2,3,1,2,4,3] and s = 7,
the subarray [4,3] has the minimal length under the problem constraint.
More practice: If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n).
Java Solution
public int minSubArrayLen(int s, int[] nums) {
int[] sum = new int[nums.length + 1];
for(int i = 1; i < sum.length; i++)
sum[i] = sum[i - 1] + nums[i - 1];
int min = nums.length + 1;
for(int i = 0; i < nums.length; i++){
int needed = s + sum[i];
int left = i + 1;
int right = sum.length - 1;
while(left <= right){
int mid = (left + right) / 2;
if(sum[mid] == needed){
left = mid;
break;
}
if(sum[mid] < needed) left = mid + 1;
else right = mid - 1;
}
if(left < sum.length && left - i < min)
min = left - i;
}
return min == nums.length + 1 ? 0 : min;
}
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