303. Range Sum Query - Immutable

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Example:

登录后复制

      
      

       
       Given nums = [-2, 0, 3, -5, 2, -1]
       
       

       
       
sumRange(0, 2) 1
       
       
sumRange(2, 5) -1
       
       
sumRange(0, 5) -3
      
      
      
      

       
       
1.
       
       
2.
       
       
3.
       
       
4.
       
       
5.
      
      

Note:
You may assume that the array does not change.
There are many calls to sumRange function.

登录后复制

      
      

       
       public class NumArray {  
       
       
    int numArray[];  
       
       
    public NumArray(int[] nums) {  
       
       
         numArray = new int[nums.length];    
       
       
         numArray = nums.clone();  
       
       
         for(int i = 1 ; i < numArray.length ; i++)  
       
       
         {  
       
       
             numArray[i] += numArray[i-1];  
       
       
         }  
       
       
    }  
       
       

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

       
       
1.
       
       
2.
       
       
3.
       
       
4.
       
       
5.
       
       
6.
       
       
7.
       
       
8.
       
       
9.
       
       
10.
       
       
11.
       
       
12.
       
       
13.
       
       
14.
       
       
15.
       
       
16.