class Solution {
    public int getKthMagicNumber(int k) {
        //1，3，5，7，9，15，21
        if (k == 1) return 1;
        if (k == 2) return 3;
        if (k == 3) return 5;
        if (k == 4) return 7;
        int[] nums = new int[k];
        nums[0] = 1;
        nums[1] = 3;
        nums[2] = 5;
        nums[3] = 7;

        int max = 7;
        int count = 4;

        int three = 0;
        int five = 0;
        int seven = 0;

        while (count < k) {
            while (nums[three] * 3 <= max) three++;
            while (nums[five] * 5 <= max) five++;
            while (nums[seven] * 7 <= max) seven++;

            nums[count] = Math.min(Math.min(nums[three] * 3, nums[five] * 5), nums[seven] * 7);
            max = nums[count];
            count++;
        }
        return nums[k - 1];
    }
}

class Solution {
    public int getKthMagicNumber(int k) {
        int[] numList=new int[k+1];
        int p3=0,p5=0,p7=0;
        numList[0]=1;
        for(int i=1;i<k;i++){
            numList[i]=Math.min(Math.min(numList[p3]*3,numList[p5]*5),numList[p7]*7);
            if(numList[i]==numList[p3]*3) p3++;
            if(numList[i]==numList[p5]*5) p5++;
            if(numList[i]==numList[p7]*7) p7++;
        }
        return numList[k-1];
    }
}

作者：orangex
链接：https://leetcode-cn.com/problems/get-kth-magic-number-lcci/solution/di-k-ge-shu-jiu-shi-xiang-bu-tong-wei-he-san-zhi-z/
来源：力扣（LeetCode）
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