Array.prototype.flat #9

Sunny-117 · 2022-11-03T07:04:44Z

const arr = [1, [2, 3, [4, 5]], 1, 2, [6, 7]]
Array.prototype.flat = function (deep = 1) {
    let res = []
    deep--
    for (const p of this) {
        if (Array.isArray(p) && deep >= 0) {
            res = res.concat(p.flat(deep))
        } else {
            res.push(p)
        }
    }
    return res
}
console.log(arr.flat(1))

Nasuke · 2022-11-04T02:47:49Z

const arr = [1, [2, 3, [4, 5]], 1, 2, [6, 7]]
Array.prototype.falt = function () {
    return this.reduce((pre, cur) => {
        cur instanceof Array ? pre.push(...cur.falt()) : pre.push(cur)
        return pre
    }, [])
}
console.log(arr.falt());

truejiang · 2022-11-04T08:02:09Z

const arr = [1, 2, [3, 4, [5, 6]]] 
Array.prototype._flat = function (depth = Infinity) {
  --depth
  return this.reduce((prev, curr) => {
      if(Array.isArray(curr) && depth >= 0) {
          prev = prev.concat(curr._flat(depth))
      } else {
          prev.push(curr)
      }
      return prev
  }, [])
}

console.log(arr._flat())
console.log(arr._flat(1))

JiaChenHuang · 2022-11-23T09:36:47Z

const arr = [1, [2, [3, [4, [5, [6, [7, [8, [9], 10], 11], 12], 13], 14], 15], 16]]
Array.prototype.flat = function (deep = 1) {
    let res = []
    if (deep === 'Infinity') {
        this.forEach((item) => {
            if (Array.isArray(item)) {
                res = res.concat(item.flat());
            } else {
                res.push(item)
            }
        })
    } else {
        deep--
        this.forEach(item => {
            if (Array.isArray(item) && deep >= 0) {
                res = res.concat(item.flat(deep))
            } else {
                res.push(item)
            }
        })

        return res
    }

}
console.log('展开一层', arr.flat(1))
console.log('完全展开', arr.flat(Infinity))

Leadgq · 2023-01-12T03:11:30Z

Array.prototype._flat = function (depth = Infinity) {
if (!Array.isArray(this) && this.length === 0) return;
depth--;
return this.reduce((prev, cur) => {
if (Array.isArray(cur) && depth >= 0) {
prev = [...prev, ...cur._flat(depth)]
} else {
prev.push(cur);
}
return prev
}, [])
}

veneno-o · 2023-01-15T13:42:01Z

Array.prototype._flat = function (deep = 1) {
	if(deep === 0) return this;
	let res = [];
	for (const item of this) {
		if (Array.isArray(item)) {
			res = res.concat(item._flat(--deep));
		} else {
			res.push(item);
		}
	}
	return res;
};
const arr = [12, 2, 4, [1, 3, [2, 34,[34,5]]]];

console.log(arr._flat(0));
console.log(arr._flat(1));
console.log(arr._flat(2));
console.log(arr._flat(Infinity));

litt1esea · 2023-01-28T06:25:06Z

const arr = [1, [2, 3, [4, 5]], 1, 2, [6, 7]]


Array.prototype._flat = function (deep = 1) {
    let res = []
    deep--
    for (const p of this) {
        if (Array.isArray(p) && deep >= 0) {
            res = res.concat(p._flat(deep))
        } else {
            res.push(p)
        }
    }
}

const val = [1, 2, [3, 4, [5, 6]]] .flat()
console.log(val);

jlx2002 · 2023-02-02T09:14:17Z

1. 递归解法

递归的思路很简单，遍历数组，如果数组内部出现数组，进行递归操作，
直到不是数组类型或者层数达到所给参数的阈值，加入到答案数组中。

/**
 * @description: 递归解决 数组扁平化flat
 * @param {*} nums
 * @param {*} deepth
 * @return {*}
 */
function flat1(nums, deepth = 1){
    // 如果是 无穷大，默认20层
    if(deepth === Infinity){
        deepth = 20;
    }
    // 校验参数
    if(deepth <= 0){
        return nums;
    }
    const result = [];
    function flats(arr, deep){
        arr.forEach(element => {
            // 控制递归条件
            if(Array.isArray(element) && deep > 0){
                flats(element, deep - 1);
            }else{
                result.push(element)
            }            
        });
    }
    flats(nums,deepth)
    return result;
}

2. 迭代解法

递归转迭代一般就比较难思考，这里我们可以引入一个队列的概念，栈也可以（但是栈的思考方式不太好想），
层数最多有deepth 层，于是，可以把每层想象成一个状态，每次检查这个状态，并更新即可。

/**
 * @description: 迭代 解决数组扁平化flat
 * @param {*} nums
 * @param {*} deepth
 * @return {*}
 */
function flat2(nums, deepth = 1){
    // 如果是 无穷大，默认20层
    if(deepth === Infinity){
        deepth = 20;
    }
    // 校验参数
    if(deepth <= 0){
        return nums;
    }
    //  用队列层数的思想代替递归
    const queue =  [...nums];
    let deep = 0;
    while(deep <= deepth){
        deep += 1;
        for(let i = 0, n = queue.length;i < n; i ++) {
            const top = queue.shift(); // 取出队头元素
            // 如果队头元素是数组
            if(Array.isArray(top) && deep <= deepth){
                // 展开后进行入队
                queue.push(...top);
            }else{
                // 如果不是array, 直接入队
                queue.push(top)
            }
        }
    }
    return queue;
}

Stream-web · 2023-02-05T02:46:45Z

const flatten = (arr) => arr.toString().split(',').map((item) => +item);

ych-chen · 2023-02-11T07:21:33Z

reduce方法

const arr2 = [0, 1, 2, [[[3, 4]]]];

function _flat(arr, depth){
    if( !Array.isArray(arr) || depth <= 0){
        return arr;
    }
    return arr.reduce((prev,cur) => {
        if(Array.isArray(cur)){
            return prev.concat(_flat(cur,depth-1));
        } else {
            return prev.concat(cur);
        }
    },[]);
}

_flat(arr2,3)

zzyyhh22lx · 2023-02-14T14:26:58Z

// Array.prototype.flat() 扁平化数组，参数代表展开的层数(默认1)
const arr = [1,2,[3,[4]]];
arr.flat(Infinity) // [1,2,3,4]

/**
 * 无副作用(不会改变原数组)
 * @param {*} depth 
 */
Array.prototype._flat = function (depth = 1) {
    return this.reduce((acc, cur) => { // 前一个值，当前值
        cur instanceof Array ? (function() { // 只能是表达式
            if(depth-- > 0) acc.push(...cur._flat(depth))
            else acc.push(cur)
        })() : acc.push(cur);
        return acc;
    }, [])
}
console.log(arr._flat(Infinity))

Tsuizen · 2023-02-15T06:21:55Z

function flatten(arr, deep) {
  while (arr.some(item => Array.isArray(item)) && deep) {
    arr = [].concat(...arr);
    deep--;
  }
  return arr;
}

sv-98-maxin · 2023-02-16T15:56:59Z

Array.prototype.myFlat = function (depth = 1) {
  const flat = arr => {
    return arr.reduce((prev, next) => {
      if (Array.isArray(next)) {
        prev.push(...next)
      } else {
        prev.push(next)
      }
      return prev
    }, [])
  }
  let res = this
  while (depth > 0) {
    res = flat(res)
    depth--
  }
  return res
}

bearki99 · 2023-02-19T12:31:00Z

Array.prototype.myFlat = function (deep = Infinity) {
  let res = [];
  deep--;
  this.forEach((item) => {
    if (Array.isArray(item) && deep >= 0) {
      res = res.concat(item.myFlat(deep));
    } else {
      res.push(item);
    }
  });
  return res;
};

kangkang123269 · 2023-02-20T06:52:07Z

Array.prototype.myFlat = function(depth = 1) {
  if (depth < 1) {
    return this.slice();
  }
  return this.reduce((acc, val) => {
    if (Array.isArray(val)) {
      acc.push(...val.myFlat(depth - 1));
    } else {
      acc.push(val);
    }
    return acc;
  }, []);
};

LifeIsTerrible · 2023-02-26T13:19:36Z

Array.prototype._flat = function (deep = 1) {
    let result = []
    deep--;
    for (let p of this) {
        if (Array.isArray(p) && deep >= 0) {
            result = result.concat(p._flat(deep))
        } else {
            result = result.push(p)
        }
    }
    return result;
}

Bbbtt04 · 2023-03-12T05:07:46Z

const arr = [1, [2, 3, [4, 5]], 1, 2, [6, 7]]

Array.prototype.flat = function (deep = 1) {
  let result = []
  for (let item of this) {
    if (Array.isArray(item) && deep >= 1) {
      result = result.concat(item.flat(--deep))
    } else {
      result.push(item)
    }
  }
  return result
}

console.log(arr.flat(2));

xun-zi · 2023-03-13T02:12:35Z

/**
     * @deep 表示只保证deep + 1层内进行数组扁平化
     * const arr = [1, [2, [3]]];
     *  console.log(arr.flat(1));
    */

    const arr = [1, [2, 3, [4, 5]], 1, 2, [6, 7]]
    Array.prototype.flat = function (deep = 1) {
        //deep表示递归了到的层数，可以想象成deep是嵌套层的下标
        deep--;
        const res = []
        for (let p of this) {
            if (Array.isArray(p) && deep >= 0) {
                //res.concat(p.flat(deep)); concat不会修改原来的值 error
                res = res.concat(p.flat(deep));
            } else {
                res.push(p);
            }
        }
        return res;
    }
    console.log(arr.flat(1));

spicylemonhaha · 2023-05-05T14:10:23Z

cscty · 2023-06-14T08:44:03Z

Array.prototype.flat = function (deep = 1) {
const res = []
for (let item of this) {
if (Array.isArray(item) && deep >= 1) {
res.push(...item.flat(deep - 1))
} else {
res.push(item)
}
}
return res
}

QdabuliuQ · 2023-07-01T14:11:45Z

   Array.prototype.flat = function(deep = 1) {
      if(deep <= 0) return this
      const _flat = (arr, deep) => {
        if(deep <= 0) return arr
        let res = []
        for(let item of arr) {
          if(Array.isArray(item)) {
            res.push(..._flat(item, deep-1))
          } else {
            res.push(item)
          }
        }
        return res
      }
      return _flat(this, deep)
    }
    console.log([1,2,3,4,[5,6,7,[99, 100]], [8,9]].flat(1));

why-ztc · 2023-08-17T08:43:48Z

const flat = arr => {
  const res = []
  const dfs = list => {
    for (const item of list) {
      if (Array.isArray(item)) {
        dfs(item)
      }else {
        res.push(item)
      }
    }
  }
  dfs(arr)
  return res
}

gswysy · 2024-03-24T12:25:47Z

Array.prototype.myFlat = function (deep = 1) {
    let res = []
    deep--
    for (const item of this) {
        if (Array.isArray(item) && deep >= 0) {
            res.push(...item.myFlat(deep))
        } else {
            res.push(item)
        }
    }
    return res
}

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Array.prototype.flat #9

Array.prototype.flat #9

Sunny-117 commented Nov 3, 2022

Nasuke commented Nov 4, 2022 •

edited

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truejiang commented Nov 4, 2022 •

edited

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JiaChenHuang commented Nov 23, 2022

Leadgq commented Jan 12, 2023

veneno-o commented Jan 15, 2023

litt1esea commented Jan 28, 2023

jlx2002 commented Feb 2, 2023

Stream-web commented Feb 5, 2023 •

edited

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ych-chen commented Feb 11, 2023

zzyyhh22lx commented Feb 14, 2023

Tsuizen commented Feb 15, 2023

sv-98-maxin commented Feb 16, 2023

bearki99 commented Feb 19, 2023

kangkang123269 commented Feb 20, 2023

LifeIsTerrible commented Feb 26, 2023

Bbbtt04 commented Mar 12, 2023

xun-zi commented Mar 13, 2023

spicylemonhaha commented May 5, 2023

cscty commented Jun 14, 2023

QdabuliuQ commented Jul 1, 2023

why-ztc commented Aug 17, 2023

gswysy commented Mar 24, 2024

Array.prototype.flat #9

Array.prototype.flat #9

Comments

Sunny-117 commented Nov 3, 2022

Nasuke commented Nov 4, 2022 • edited Loading

truejiang commented Nov 4, 2022 • edited Loading

JiaChenHuang commented Nov 23, 2022

Leadgq commented Jan 12, 2023

veneno-o commented Jan 15, 2023

litt1esea commented Jan 28, 2023

jlx2002 commented Feb 2, 2023

1. 递归解法

2. 迭代解法

Stream-web commented Feb 5, 2023 • edited Loading

ych-chen commented Feb 11, 2023

zzyyhh22lx commented Feb 14, 2023

Tsuizen commented Feb 15, 2023

sv-98-maxin commented Feb 16, 2023

bearki99 commented Feb 19, 2023

kangkang123269 commented Feb 20, 2023

LifeIsTerrible commented Feb 26, 2023

Bbbtt04 commented Mar 12, 2023

xun-zi commented Mar 13, 2023

spicylemonhaha commented May 5, 2023

cscty commented Jun 14, 2023

QdabuliuQ commented Jul 1, 2023

why-ztc commented Aug 17, 2023

gswysy commented Mar 24, 2024

Nasuke commented Nov 4, 2022 •

edited

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truejiang commented Nov 4, 2022 •

edited

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Stream-web commented Feb 5, 2023 •

edited

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