Subarray Sum Closest(lintcode 139)

Description

Given an integer array, find a subarray with sum closest to zero. Return the indexes of the first number and last number.

Example

Given [-3, 1, 1, -3, 5], return [0, 2], [1, 3], [1, 1], [2, 2] or [0, 4].

Interface

public class Solution {
    /**
     * @param nums: A list of integers
     * @return: A list of integers includes the index of the first number 
     *          and the index of the last number
     */
    public int[] subarraySumClosest(int[] nums) {
        // write your code here
    }
}

Solution

public class Solution {
    /**
     * @param nums: A list of integers
     * @return: A list of integers includes the index of the first number 
     *          and the index of the last number
     */
    public int[] subarraySumClosest(int[] nums) {
        // write your code here
        int[] res = new int[2];

        if (nums == null || nums.length == 0) {
            return res;
        }

        if (nums.length == 1) {
            res[0] = res[1] = 0;
            return res;
        }

        Pair[] sums = new Pair[nums.length + 1];
        sums[0] = new Pair(0, 0);
        int prev = 0;

        for (int i = 1; i <= nums.length; ++i) {
            sums[i] = new Pair(prev + nums[i - 1], i);
            prev = sums[i].sum;
        }

        Arrays.sort(sums, new Comparator<Pair>() {
            @Override
            public int compare(Pair a, Pair b) {
                return a.sum - b.sum;
            }
        });

        int min = Integer.MAX_VALUE;

        for (int i = 1; i <= nums.length; ++i) {
            if (min > sums[i].sum - sums[i - 1].sum) {
                min = sums[i].sum - sums[i - 1].sum;
                int[] temp = new int[]{sums[i].index - 1, sums[i - 1].index - 1};
                Arrays.sort(temp);
                res[0] = temp[0] + 1;
                res[1] = temp[1];
            }
        }

        return res;
    }
}

class Pair {
    int sum;
    int index;
    public Pair(int sum, int index) {
        this.sum = sum;
        this.index = index;
    }
}