JavaScript实现数组全排列、去重及求最大值算法示例

function permutation(arr){
 if (arr.length == 1)
 return arr;
 else if (arr.length == 2)
 return [[arr[0],arr[1]],[arr[1],arr[0]]];
 else {
 var temp = [];
 for (var i = 0; i < arr.length; i++) {
 var save = arr[i];
 arr.splice(i, 1);//取出arr[i]
 var res = permutation(arr);//递归排列arr[0],arr[1],...,arr[i-1],arr[i+1],...,arr[n]
 arr.splice(i, 0, save);//将arr[j]放入数组，保持原来的位置
 for (var j = 0; j < res.length; j++) {
 res[j].push(arr[i]);
 temp.push(res[j]);//将arr[j]组合起来
 }
 }
 return temp;
 }
}

function norepeat(contents) {
 var norepeatContents = [];
 for (var i = 0; i < contents.length; i++) {
 if(norepeatContents.indexOf(contents[i]) == -1)
 norepeatContents.push(contents[i]);
 }
 return norepeatContents;
}

function norepeat(contents) {
 var norepeatContents = [], hash = {};
 for (var i = 0; i < contents.length; i++) {
 if(!hash[contents[i]]) {
 norepeatContents.push(contents[i]);
 hash[contents[i]] = true;
 }
 }
 return norepeatContents;
}

function findMax(arr) {
 var max = arr[0];
 for (var i = 1; i < arr.length; i++) {
 if (arr[i] > max)
 max = arr[i];
 }
 return max;
}

function findMax(arr) {
 return Math.max.apply(Math, arr);
}