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package g0301_0400.s0303_range_sum_query_immutable;

// #Easy #Array #Design #Prefix_Sum #Programming_Skills_I_Day_12_Class_and_Object
// #2022_07_07_Time_7_ms_(100.00%)_Space_44.9_MB_(96.34%)

/**
 * 303 - Range Sum Query - Immutable\.
 *
 * Easy
 *
 * Given an integer array `nums`, handle multiple queries of the following type:
 *
 * 1.  Calculate the **sum** of the elements of `nums` between indices `left` and `right` **inclusive** where `left <= right`.
 *
 * Implement the `NumArray` class:
 *
 * *   `NumArray(int[] nums)` Initializes the object with the integer array `nums`.
 * *   `int sumRange(int left, int right)` Returns the **sum** of the elements of `nums` between indices `left` and `right` **inclusive** (i.e. `nums[left] + nums[left + 1] + ... + nums[right]`).
 *
 * **Example 1:**
 *
 * **Input**
 *
 *     ["NumArray", "sumRange", "sumRange", "sumRange"]
 *     [[[-2, 0, 3, -5, 2, -1]], [0, 2], [2, 5], [0, 5]]
 *
 * **Output:** [null, 1, -1, -3]
 *
 * **Explanation:**
 *
 *     NumArray numArray = new NumArray([-2, 0, 3, -5, 2, -1]);
 *     numArray.sumRange(0, 2); // return (-2) + 0 + 3 = 1
 *     numArray.sumRange(2, 5); // return 3 + (-5) + 2 + (-1) = -1
 *     numArray.sumRange(0, 5); // return (-2) + 0 + 3 + (-5) + 2 + (-1) = -3 
 *
 * **Constraints:**
 *
 * *   1 <= nums.length <= 10⁴
 * *   -10⁵ <= nums[i] <= 10⁵
 * *   `0 <= left <= right < nums.length`
 * *   At most 10⁴ calls will be made to `sumRange`.
**/
public class NumArray {
    private int[] sums;

    public NumArray(int[] nums) {
        sums = new int[nums.length];
        for (int i = 0; i < nums.length; i++) {
            if (i == 0) {
                sums[i] = nums[i];
            } else {
                sums[i] = sums[i - 1] + nums[i];
            }
        }
    }

    public int sumRange(int i, int j) {
        if (i == 0) {
            return sums[j];
        }
        return sums[j] - sums[i - 1];
    }
}

/*
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(left,right);
 */