Leetcode题目：Range Sum Query

题目：

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

Example:

Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

Note:

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

题目解答：这个题目说了，会反复的求一段数字的和，但是默认数组不变。这么说来，就是求和的复杂度就是主要的复杂度。那么可以先把它们存起来，然后再求得时候，直接把结果返回来。需要注意的是，求[2,5]的和就是求[0，5]的和减去[0,2]的和，再加上[2]这个位置的值。

代码如下：

class NumArray {
public:
    NumArray(vector<int> &nums):nums(nums) {
        int sum = 0;
        for(int i = 0;i < nums.size();i++)
        {
            sum += nums[i];
            sums.push_back(sum);
        }
    }

int sumRange(int i, int j) {
        if((i > j) || (i >= nums.size()) || (j >= nums.size()))
            return 0;
        return sums[j] - sums[i] + nums[i];
    }

private:
vector<int> sums;
vector<int> &nums;
};

// Your NumArray object will be instantiated and called as such:
// NumArray numArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);

转载于:https://www.cnblogs.com/CodingGirl121/p/5477231.html

Leetcode题目：Range Sum Query - Immutable相关推荐

leetcode 303. Range Sum Query - Immutable | 303. 区域和检索 - 数组不可变（一维前缀和问题）
题目 https://leetcode.com/problems/range-sum-query-immutable/ 题解标准的前缀和问题,简单题,不多说,直接上代码 import java.ut ...
[LeetCode] 303. Range Sum Query - Immutable
https://leetcode.com/problems/range-sum-query-immutable/ 用一个 sum 数组,sum[i] -- nums 中选出前 i 个元素,求和所得到的 ...
LeetCode 303. Range Sum Query - Immutable
题目: Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclu ...
leetcode 304. Range Sum Query 2D - Immutable |304. 二维区域和检索 - 矩阵不可变（二维前缀和问题）
题目 https://leetcode.com/problems/range-sum-query-2d-immutable/ 题解本题是 medium 难度,二维前缀和问题.相似题目有: Easy: ...
数据结构线段树介绍与笔试算法题-LeetCode 307. Range Sum Query - Mutable--Java解法
此文首发于我的个人博客:zhang0peter的个人博客 LeetCode题解文章分类:LeetCode题解文章集合 LeetCode 所有题目总结:LeetCode 所有题目总结线段树(Segme ...
[Leetcode] 304. Range Sum Query 2D - Immutable 解题报告
题目: Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper ...
LeetCode Range Sum Query Immutable
2131231 转载于:https://www.cnblogs.com/ZHONGZHENHUA/p/10873807.html
303. Range Sum Query - Immutable
题目: Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclu ...
重拾编程之路--jeetcode(java)--Range Sum Query - Immutable
算法理解: 1)用一个和数组记录前几个元素的和: sum[0]---(0,0)的和: sum[1]-- (0,1)的和: ...

Leetcode题目：Range Sum Query - Immutable

Leetcode题目：Range Sum Query - Immutable相关推荐

最新文章

热门文章