[LintCode] 1844. subarray sum equals k II

public class Solution {
    /**
     * @param nums: a list of integer
     * @param k: an integer
     * @return: return an integer, denote the minimum length of continuous subarrays whose sum equals to k
     */
    public int subarraySumEqualsKII(int[] nums, int k) {
        // write your code here
        int[] prefix = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            if (i == 0) {
                prefix[i] = nums[i];
                continue;
            }
            prefix[i] = prefix[i - 1] + nums[i];
        }
        System.out.println(Arrays.toString(prefix));
        
        int res = Integer.MAX_VALUE;
        for (int i = 0; i < nums.length; i++) {
            for (int j = i; j < nums.length; j++) {
                if (i == 0) {
                    if (prefix[j] == k) {
                        res = Math.min(res, j + 1);
                    }
                    continue;
                }
                if (prefix[j] - prefix[i - 1] == k) {
                    res = Math.min(res, j - i + 1);
                }
            }
        }
        return res == Integer.MAX_VALUE ? -1 : res;
    }
}

public class Solution {
    /**
     * @param nums: a list of integer
     * @param k: an integer
     * @return: return an integer, denote the minimum length of continuous subarrays whose sum equals to k
     */
    public int subarraySumEqualsKII(int[] nums, int k) {
        // write your code here
        Map<Integer, Integer> map = new HashMap<>();
        int sum = 0;
        int res = Integer.MAX_VALUE;
        map.put(0, -1);
        
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (map.containsKey(sum - k)) {
                // actually get the i - 1 index for  map.get(sum - k)
                res = Math.min(res, i - map.get(sum - k));
            }
            map.put(sum, i);
        }
        return res == Integer.MAX_VALUE ? -1 : res;
    }
}