第 161 题：用最精炼的代码实现数组非零非负最小值index

[libin1991]

例如：[10,21,0,-7,35,7,9,23,18] 输出5, 7最小

function getIndex(arr){
      let index=null;
      ...
      return index;
}

[slogeor]

/**
 * @description 用最精炼的代码实现数组非零最小值 index
 * @param {array} arr 数组
 * @returns {number} index 索引
 */
function getIndex(arr) {
      let index = -1;
      const minVal = arr.reduce((cur, pre) => {
            return (cur <= 0 || pre <= 0) ? Math.max(cur, pre) : cur > pre ? pre : cur;
      }, -1);
      index = arr.findIndex(item => item == minVal && minVal > 0)
      return index;
}

[libin1991]

@slogeor reduce和reduce一起复杂度是多少？ 没有体现最精炼

[slogeor]

@libin1991 上面的时间复杂度是 O(N^2),

function getIndex(arr) {
      let index = -1;
      arr.reduce((pre, cur, k) => {
            if (cur <= 0 || pre <= 0) {
                  index = cur <= 0 && pre <= 0 ? -1 : cur > pre ? k : index;
            } else {
                  index = cur > pre ? index : k;
            }
            return cur > pre ? pre : cur;
      }, -1);
      return index;
}

时间复杂度是 O(N)

[tanxin03]

import postwroker from 'worker-loader!./postworker'
有人知道加!这种引入方法是什么意思吗

[slogeor]

@tanxin520 上下文方便说一下嘛

[tanxin03]

https://www.webpackjs.com/loaders/worker-loader/
您访问下这个地址，这上面有这个demo，但是没讲这个！的意思，我想了解一下，麻烦了 @slogeor

[slogeor]

const arr = [10, 21, 0, -7, 35, 7, 9, 23, 18];

function findMinimumIndex(arr) {
  return arr.findIndex(item => item === arr.filter(item => item > 0).sort((a, b) => a - b)[0])
}
console.log(findMinimumIndex(arr))

这个时间复杂度也不低

[slogeor]

@libin1991 楼主，我是否可以贡献一题，实现 JSON.stringify 方法

[libin1991]

@libin1991 上面的时间复杂度是 O(N^2),

function getIndex(arr) {
      let index = -1;
      arr.reduce((pre, cur, k) => {
            if (cur <= 0 || pre <= 0) {
                  index = cur <= 0 && pre <= 0 ? -1 : cur > pre ? k : index;
            } else {
                  index = cur > pre ? index : k;
            }
            return cur > pre ? pre : cur;
      }, -1);
      return index;
}

时间复杂度是 O(N)

function getIndex(arr) {
      let index = -1;
      arr.reduce((pre, cur, k) => {
            if (cur <= 0 || pre <= 0) {
                  index = cur <= 0 && pre <= 0 ? -1 : cur > pre ? k : index;
            } else {
                  index = cur > pre ? index : k;
            }
            return cur > pre ? pre : cur;
      }, -1);
      return index;
}

输出答案都是错的！

getIndex([10,21,0,-7,35,7,9,23,18])
// 8

[slogeor]

@libin1991 上面的时间复杂度是 O(N^2),

function getIndex(arr) {
      let index = -1;
      arr.reduce((pre, cur, k) => {
            if (cur <= 0 || pre <= 0) {
                  index = cur <= 0 && pre <= 0 ? -1 : cur > pre ? k : index;
            } else {
                  index = cur > pre ? index : k;
            }
            return cur > pre ? pre : cur;
      }, -1);
      return index;
}

时间复杂度是 O(N)

function getIndex(arr) {
      let index = -1;
      arr.reduce((pre, cur, k) => {
            if (cur <= 0 || pre <= 0) {
                  index = cur <= 0 && pre <= 0 ? -1 : cur > pre ? k : index;
            } else {
                  index = cur > pre ? index : k;
            }
            return cur > pre ? pre : cur;
      }, -1);
      return index;
}

输出答案都是错的！

getIndex([10,21,0,-7,35,7,9,23,18])
// 8

调整了一下

function getIndex(arr) {
    if (!arr.length) return -1;
    let index = -1;
    arr.reduce((pre, next, k) => {
        const min = Math.min(pre, next);
        const max = Math.max(pre, next, 0);
        // 都是正数
        if (pre > 0 && next > 0) {
            index = min === pre ? index : k
            return min;
        }

        index = (max === 0 ||  max === pre) ? index : k;
        return max;
    }, 0)
    return index;
}

[slogeor]

常规写法

function rankVoteMaxIndex(arr) {
            let itemIndex = 0;   // 非0最小index
            let itemRank=0;      // 非0最小值
            let length=arr.length;
            if(!length){
                 return -1;
            }
            for(let i=0;i<length;i++){
                let item=arr[i];
                if(item<0) continue;
                if(!itemRank) {
                    itemIndex = i;
                    itemRank = item;
                }
                if(item < itemRank ){
                    itemIndex = i;
                    itemRank = item;
                }
               
            }
            return itemIndex;
        }

这个答案面试官给了65分（满分100）

rankVoteMaxIndex([-1] // 0
rankVoteMaxIndex([-1, 0, 1] // 0

[libin1991]

<script>

    function rankVoteMaxIndex(arr) {
        let itemIndex = -1;   // 非0最小index
        let itemRank = -1;      // 非0最小值
        let length = arr.length;
        if (!length) {
            return itemIndex;
        }
        for (let i = 0; i < length; i++) {
            let item = arr[i];
            if (item > 0) {
                if (itemRank < 0) {
                    itemIndex = i;
                    itemRank = item;
                }
                if (item < itemRank) {
                    itemIndex = i;
                    itemRank = item;
                }
            }

        }
        return itemIndex < 0 ? -1 : itemIndex;
    }

    // rankVoteMaxIndex([-1] // 0
    // rankVoteMaxIndex([-1, 0, 1] // 0

    console.log(rankVoteMaxIndex([-1]));
    console.log(rankVoteMaxIndex([-1, 0, 1]));
    console.log(rankVoteMaxIndex([10, 21, 0, -7, 35, 7, 9, 23, 18]))
    console.log(rankVoteMaxIndex([0, 10, 21, 0, -7, 35, 7, 9, 23, 18]))
</script>

[XuedaoYuan]

会不会B格不够高

const arr = [-10, 0, 10, 21, 0, -7, 35, 7, 9, 23, 18]
let minNum
let minIndex = -1
for (let i = 0, len = arr.length; i < len; i++) {
	if (minNum) {
		if (arr[i] < minNum && arr[i] > 0) {
			minNum = arr[i]
			minIndex = i
		}
	} else {
		if (arr[i] > 0) {
			minNum = arr[i]
			minIndex = i
		}
	}
}

console.log(minIndex, minNum)