BiruLyu
7/29/2017 - 6:46 PM

## 209. Minimum Size Subarray Sum(#).java

``````public class Solution {
public int minSubArrayLen(int s, int[] nums) {
return solveNLogN(s, nums);
}

private int solveN(int s, int[] nums) {
int start = 0, end = 0, sum = 0, minLen = Integer.MAX_VALUE;
while (end < nums.length) {
while (end < nums.length && sum < s) sum += nums[end++];
if (sum < s) break;
while (start < end && sum >= s) sum -= nums[start++];
if (end - start + 1 < minLen) minLen = end - start + 1;
}
return minLen == Integer.MAX_VALUE ? 0 : minLen;
}

private int solveNLogN(int s, int[] nums) {
int[] sums = new int[nums.length + 1];
for (int i = 1; i < sums.length; i++) sums[i] = sums[i - 1] + nums[i - 1];
int minLen = Integer.MAX_VALUE;
for (int i = 0; i < sums.length; i++) {
int end = binarySearch(i + 1, sums.length - 1, sums[i] + s, sums);
if (end == sums.length) break;
if (end - i < minLen) minLen = end - i;
}
return minLen == Integer.MAX_VALUE ? 0 : minLen;
}

private int binarySearch(int lo, int hi, int key, int[] sums) {
while (lo <= hi) {
int mid = (lo + hi) / 2;
if (sums[mid] >= key){
hi = mid - 1;
} else {
lo = mid + 1;
}
}
return lo;
}
}``````
``````/*Sliding Window*/
public class Solution {
public int minSubArrayLen(int s, int[] nums) {
if (nums == null || nums.length < 1) return 0;
int start = 0;
int len = nums.length;
int sum = 0;
int res = len + 1;
for (int end = 0; end < len; end++) {
sum += nums[end];
while (sum >= s) {
res = Math.min(res, end - start + 1);
sum -= nums[start++];
}
}
return res == len + 1 ? 0 : res;
}
}``````