Solution.java

/**
 * Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.
 *
 * Example 1:
 *
 * Input:nums = [1,1,1], k = 2
 * Output: 2
 *
 * Note:
 *
 *     The length of the array is in range [1, 20,000].
 *     The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].
 *
 */

class Solution {
    public int subarraySum(int[] nums, int k) {
        int[] sums = new int[nums.length + 1];
        sums[0] = 0;
        for (int i = 0; i < nums.length; i++) {
            sums[i + 1] = sums[i] + nums[i];
        }
        int ret = 0;
        for (int i = 0; i < nums.length; i++) {
            for (int j = i + 1; j <= nums.length; j++) {
                if (sums[j] - sums[i] == k) {
                    ret++;
                }
            }
        }
        return ret;
    }
}