全排列

/**
 * 回溯算法
 */
const fullPermutationByFor = (nums = [1,2,3]) => {
    const res = []
    const backTrack = (path) => {
        if(path.length === nums.length){
            res.push(path)
            return path
        }
        for(let i = 0; i < nums.length; i++){
            const item = nums[i]
            if(path.includes(item)) {
                continue
            }
            backTrack(path.concat(item))
        }
    }
    backTrack([])
    return res
}

const fullPermutationByForEach = (nums = [1,2,3]) => {
    const res = []
    const backTrack = (path) => {
        if(path.length === nums.length){
            res.push(path)
            return path
        }
        nums.forEach(num => {
            if(path.includes(num)) {
                // forEach无法跳出循环 api机制 此处逻辑代表不执行下面代码
                return
            }
            backTrack(path.concat(num))
        })
    }
    backTrack([])
    return res
}