算法导论：计算“1”的个数

 1 package org.warnier.zhang.demo;
 2 
 3 public class OneCalculator {
 4     
 5     public int calculate(int n) {
 6         int count = 0;
 7         for(int i = 1; i <= n; i++){
 8             int z = i;
 9             while(z != 0){
10                 if(z % 10 == 1){
11                     count++;
12                 }
13                 z /= 10;
14             }
15         }
16         return count;
17     }
18 
19 }

 1 package org.warnier.zhang.demo.test;
 2 
 3 import static org.junit.Assert.*;
 4 import org.junit.Before;
 5 import org.junit.Test;
 6 import org.warnier.zhang.demo.OneCalculator;
 7 
 8 public class OneCalculatorTest {
 9 
10     @Before
11     public void setUp() throws Exception {
12     }
13     
14     @Test
15     public void test_n_equals_1_return_1(){
16         OneCalculator calculator = new OneCalculator();
17         int actual = calculator.calculate(1);
18         int expected = 1;
19         assertEquals(expected, actual);
20     }
21     
22     @Test
23     public void test_n_equals_10_return_2(){
24         OneCalculator calculator = new OneCalculator();
25         int actual = calculator.calculate(10);
26         int expected = 2;
27         assertEquals(expected, actual);
28     }
29     
30     @Test
31     public void test_n_equals_11_return_4(){
32         OneCalculator calculator = new OneCalculator();
33         int actual = calculator.calculate(11);
34         int expected = 4;
35         assertEquals(expected, actual);
36     }
37     
38     @Test
39     public void test_n_equals_12_return_5(){
40         OneCalculator calculator = new OneCalculator();
41         int actual = calculator.calculate(12);
42         int expected = 5;
43         assertEquals(expected, actual);
44     }
45 
46 }