JavaScript算法题（1）—— Return Largest Numbers in Arrays

Return an array consisting of the largest number from each provided sub-array. For simplicity, the provided array will contain exactly 4 sub-arrays.

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);

1. Basic Code Solution

function largestOfFour(arr) {
  var results = [];
  for(var i = 0; i < arr.length; i++){
    var largestNumber = 0;
    for(var j = 0; j < arr[i].length; j++){
      if(arr[i][j] > largestNumber) {
        largestNumber = arr[i][j];
      }
    }
    results[i] = largestNumber;
  }
  return results;
}

算法说明：

• 创建results变量存储返回的结果数组；
• 创建一个外部循还遍历外层数组；
  • 创建内层循还遍历每一个内层数组，寻找最大值，存储在变量largestNumber中；
  • 将每一个内层数组中的最大值保存在results中的相应位置；
• 返回结果数组。

2. Intermediate Code Solution

function largestOfFour(arr) {
  return arr.map(function(group){
    return group.reduce(function(prev, current) {
      return (current > prev) ? current:prev;
    },0);
  });
}

• Array.prototype.map()

• Array.prototype.reduce()

• Ternary Operators(三元运算)

3. Advanced Code Solution

function largestOfFour(arr) {
  return arr.map(Function.apply.bind(Math.max, null));
}

• Function.prototype.apply()
• Function.prototype.bind()