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Geek-James opened this issue Aug 28, 2019 · 0 comments
Open

寻找数组的中心索引 #32

Geek-James opened this issue Aug 28, 2019 · 0 comments
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算法 About algorithm

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@Geek-James
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Geek-James commented Aug 28, 2019

给定一个整数类型的数组 nums,请编写一个能够返回数组“中心索引”的方法。

我们是这样定义数组中心索引的:数组中心索引的左侧所有元素相加的和等于右侧所有元素相加的和。

如果数组不存在中心索引,那么我们应该返回 -1。如果数组有多个中心索引,那么我们应该返回最靠近左边的那一个。

示例 1:

输入: 
nums = [1, 7, 3, 6, 5, 6]
输出: 3

解释:
索引3 (nums[3] = 6) 的左侧数之和(1 + 7 + 3 = 11),与右侧数之和(5 + 6 = 11)相等。
同时, 3 也是第一个符合要求的中心索引。
示例 2:

输入: 
nums = [1, 2, 3]
输出: -1

解释:
数组中不存在满足此条件的中心索引。
说明:

nums 的长度范围为 [0, 10000]。
任何一个 nums[i] 将会是一个范围在 [-1000, 1000]的整数。

方法一:

var pivotIndex = function(nums) {
    
     if(nums.length < 3) return -1;
    let sum=0 , left =0 ,len = nums.length

    for (let i=0;i<len;i++) {
        sum+=nums[i];
    }

    for(let i=0; i<len; i++){
        if((sum-nums[i])/2 ==left){
            return i;
        }
        left+=nums[i]
    }
    return -1;
  
};
@Geek-James Geek-James added the 算法 About algorithm label Aug 28, 2019
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