剑指offer 34_丑数

 

丑数：只有2 3 5 这三个因子的数，求前（第）1500个。习惯上我们把1当作第一个丑数

例如 6, 8是丑数。14不是。

 

#include <stdio.h>

int Min(int x,int y, int z){
        int min = (x <= y) ? x : y;
        return min = (z <= min) ? z : min;
}


int GetUglyNumber(int index){
    if(index <= 0){
        return 0;
    }

    int* uglyNumbers= new int[index];
    int uglyCount = 1;
    uglyNumbers[0] = 1;

    int* ugly2 = uglyNumbers;
    int* ugly3 = uglyNumbers;
    int* ugly5 = uglyNumbers;

    for(; uglyCount< index; ++uglyCount){
        int min = Min((*ugly2)*2,(*ugly3)*3,(*ugly5)*5);
        uglyNumbers[uglyCount] = min;

        while((*ugly2)*2 <= min){
            ++ugly2;
        }
        while((*ugly3)*3 <= min){
            ++ugly3;
        }
        while((*ugly5)*5 <= min){
            ++ugly5;
        }
    }

    for(int i=0; i<index; i++){
        printf("%d\n",uglyNumbers[i]);
    }

    delete[] uglyNumbers;
}

int main(){
    int index = 1500;
    GetUglyNumber(index);
    return 0;
}

 

gcc uglyNumber.cpp

 

1
2
3
4
5
6
8
9
10
12
15
16
18
20
24
25
27
30
32
36

.

.

.

786432000
787320000
791015625
796262400
797161500
800000000
805306368
806215680
810000000
816293376
819200000
820125000
829440000
838860800
839808000
843750000
849346560
850305600
854296875
859963392

 

 

第1500个为 859963392