题解 | 第k个数

#include <algorithm>
#include <vector>
class KthNumber {
public:
    int findKth(int k) {
        // write code here
        vector<int> res(k+1);
        res[0] =1;
        int i3=0,i5=0,i7=0;
        for(int i=1;i<k+1;i++)
        {
            int next3 = res[i3]*3;
            int next5= res[i5]*5;
            int next7 = res[i7]*7;
            int next = min(next3, min(next5,next7));
            res[i] = next;
            if(next == next3) i3++;
            if(next == next5) i5++;
            if(next == next7) i7++;
        }
        return res[k];
    }
};