Leetcode Perfect Squares

第一題bfs + 圖 , 效率很低

pesudo code :

make a queue
make a visited map 

push [n,0] into queue  // [n,0] means [currentNumRemain , stepsCount]

while queue is not empty
    pop pairs
    currnumRemain = pairs[0]
    steps = pairs[1]
    iterate from 0 until i*i<=currentNum
        if currNum-i*i==0
            return step+1

        if i*i already visited    // 因為已經有其他路徑先到達了
            pass
        else 
            push [currNum-i*i,step+1] into queue

func numSquares(n int) int {
    q:=[][]int{}
    vm:=make(map[int]int)
    q=append(q,[]int{n,0})

    for len(q)!=0 {
        //pop pairs
        pairs:=q[0]
        q=q[1:]

        currNumRemain:=pairs[0]
        steps:=pairs[1]

        for i:=0;i*i<=currNumRemain;i++ {
            if currNumRemain-i*i==0 {
                return steps+1
            }
            if _,ok:=vm[i*i];ok {
                continue
            } else {
                q=append(q,[]int{currNumRemain-i*i,steps+1})
            }
        }
    }
    return 0
}

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