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1523. 在区间范围内统计奇数数目

English Version

题目描述

给你两个非负整数 low 和 high 。请你返回 low 和 high 之间（包括二者）奇数的数目。

 

示例 1：

输入：low = 3, high = 7
输出：3
解释：3 到 7 之间奇数数字为 [3,5,7] 。

示例 2：

输入：low = 8, high = 10
输出：1
解释：8 到 10 之间奇数数字为 [9] 。

 

提示：

• 0 <= low <= high <= 10^9

解法

方法一：前缀和思想

[0, x] 之间的奇数个数为 (x + 1) >> 1，那么 [low, high] 之间的奇数个数为 ((high + 1) >> 1) - (low >> 1)。

Python3

class Solution:
    def countOdds(self, low: int, high: int) -> int:
        return ((high + 1) >> 1) - (low >> 1)

Java

class Solution {
    public int countOdds(int low, int high) {
        return ((high + 1) >> 1) - (low >> 1);
    }
}

Rust

impl Solution {
    pub fn count_odds(low: i32, high: i32) -> i32 {
        ((high + 1) >> 1) - (low >> 1)
    }
}

C++

class Solution {
public:
    int countOdds(int low, int high) {
        return (high + 1 >> 1) - (low >> 1);
    }
};

Go

func countOdds(low int, high int) int {
	return ((high + 1) >> 1) - (low >> 1)
}

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