【leetcode】:Range Sum Query - Immutable

[code]public class NumArray {
    int[] sums;

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

    public int sumRange(int i, int j) {
         if(i>j || i<0 || j<0 || j>=sums.length) return 0;  
        return i==0 ? sums[j] : (sums[j] - sums[i-1]);  
    }
}