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freeCodeCamp/curriculum/challenges/chinese/10-coding-interview-prep/rosetta-code/equilibrium-index.chinese.md
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title, id, challengeType, videoUrl, localeTitle
title id challengeType videoUrl localeTitle
Equilibrium index 5987fd532b954e0f21b5d3f6 5 均衡指数

Description

序列的平衡指数是序列的索引,使得较低指数处的元素之和等于较高指数处的元素之和。

例如,在序列$ A $中

:::: $ A_0 = -7 $

:::: $ A_1 = 1 $

:::: $ A_2 = 5 $

:::: $ A_3 = 2 $

:::: $ A_4 = -4 $

:::: $ A_5 = 3 $

:::: $ A_6 = 0 $

3是均衡指数因为

:::: $ A_0 + A_1 + A_2 = A_4 + A_5 + A_6 $

6也是均衡指数因为

:::: $ A_0 + A_1 + A_2 + A_3 + A_4 + A_5 = 0 $

(零元素之和为零)

7不是均衡指数因为它不是序列$ A $的有效索引。

编写一个函数,给定一个序列,返回其平衡指数(如果有的话)。

假设序列可能很长。

Instructions

Tests

tests:
  - text: <code>equilibrium</code>是一种功能。
    testString: assert(typeof equilibrium === 'function');
  - text: '<code>equilibrium([-7, 1, 5, 2, -4, 3, 0])</code> <code>[3,6]</code> <code>equilibrium([-7, 1, 5, 2, -4, 3, 0])</code>应该返回<code>[3,6]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[0]), ans[0]);
  - text: '<code>equilibrium([2, 4, 6])</code>应该返回<code>[]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[1]), ans[1]);
  - text: '<code>equilibrium([2, 9, 2])</code>应该返回<code>[1]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[2]), ans[2]);
  - text: '<code>equilibrium([1, -1, 1, -1, 1, -1, 1])</code>应该返回<code>[0,1,2,3,4,5,6]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[3]), ans[3]);
  - text: '<code>equilibrium([1])</code>应该返回<code>[0]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[4]), ans[4]);
  - text: '<code>equilibrium([])</code>应该返回<code>[]</code> 。'
    testString: assert.deepEqual(equilibrium(equilibriumTests[5]), ans[5]);

Challenge Seed

function equilibrium (a) {
  // Good luck!
}

After Test

console.info('after the test');

Solution

// solution required