prefix sum template

ArrayUtil.java

    /**
     * Prefix sums of nums, preSum[i] = sum of range [0, j)
     * sum[i, j) = preSum[j] - preSum[i]
     *
     * @param nums
     * @return preSum array
     */
    public static int[] getPrefixSum(int[] nums) {
        int[] preSum = new int[nums.length + 1];
        for (int i = 1; i <= nums.length; i++) {
            preSum[i] = preSum[i - 1] + nums[i - 1];
        }
        return preSum;
    }