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[leetcode] problem 560 – subarray sum equals k

admin 11月 13, 2020 0

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

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].

Code

public int (int[] nums, int k) {
    int result = 0;
    int sum = 0;
    Map<Integer, Integer> map = new HashMap<>();
    map.put(0, 1);

    for (int i = 0; i < nums.length; i++) {
        sum += nums[i];

        if (map.containsKey(sum - k))
            result += map.get(sum - k);

        map.put(sum, map.getOrDefault(sum, 0) + 1);
    }

    return result;
}