Method NumArray

Java/Range-Sum-Query-Mutable.java:18–24

(int[] nums)

    int n;

    public NumArray(int[] nums) {
        if (nums.length > 0) {
            n = nums.length;
            tree = new int[n * 2];
            buildTree(nums);
        }
    }
    
    // build the segment tree and store it in array of size 2 * nums[] length
    // so the nums[] values are stores at leaves of the segment tree.