__Algorithm__

__LeetCode__ ---全排列算法.js

/**
 * Heap's algorithm
 */

 function heapPermutation(arr,size,n){
  var swap = function (index1,index2) {
      var temp = arr[index1];
      arr[index1] = arr[index2];
      arr[index2] = temp;
  }
  if (size === 1){
      console.log(arr);
      return;
  }
  for (let i = 0; i < size; i++){
      heapPermutation(arr, size -1,n);

      swap(size % 2 ? 0 : i, size - 1);
  }
}

var arr = ['a','b','c','d'];

heapPermutation(arr,arr.length,arr.length);

__LeetCode__ ---查找所有的素数.js

var prime = function(num){
  var i,j;
  var arr = [];

for(i = 1; i < num; i++){
  for(j=2; j < i; j++){
    if(i%j === 0) {
       break;
    }
  }

  if(i <= j && i !=1){
    arr.push(i);
  }

}
return arr;
};

__LeetCode__ ---辗转相除法求最大公约数.js

// 递归 
function gcd(m ,n){
  if(n) return gcd(n,m%n);
  return m;
}