Leetcode 303. Range Sum Query - Immutable

Tyan

发布于 2019-05-25 22:16:17

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文章作者：Tyan

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1. Description

2. Solution

Version 1

class NumArray {
public:
    NumArray(vector<int> nums) {
        this->nums = nums;
    }
    
    int sumRange(int i, int j) {
        int sum = 0;
        for(int index = i; index <= j; index++) {
            sum += nums[index];
        }
        return sum;
    }

private:
    vector<int> nums;
};

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

Version 2

class NumArray {
public:
    NumArray(vector<int> nums) {
        int sum = 0;
        for(int num: nums) {
            sum += num;
            sums.push_back(sum);
        }
    }
    
    int sumRange(int i, int j) {
        if(i > 0) {
            return sums[j] - sums[i - 1];
        }
        return sums[j];
    }

private:
    vector<int> sums;
};

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