leetcode/src/test/java/org/overmind/BackspaceStringCompareTest.java at main · eugene-karanda/leetcode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
package org.overmind;

import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;

/**
 * <a href="https://leetcode.com/problems/backspace-string-compare/">844. Backspace String Compare</a> (Easy)
 * <p>
 * Compare two strings after applying the backspace character {@code '#'}.
 */
public class BackspaceStringCompareTest {

  private final Solution solution = new Solution();

  @Test
  void example1() {
    // when
    var result = solution.backspaceCompare("ab#c", "ad#c");

    // then
    assertThat(result)
      .isTrue();
  }

  @Test
  void example2() {
    // when
    var result = solution.backspaceCompare("ab##", "c#d#");

    // then
    assertThat(result)
      .isTrue();
  }

  @Test
  void example3() {
    // when
    var result = solution.backspaceCompare("a#c", "b");

    // then
    assertThat(result)
      .isFalse();
  }

  class Solution {
    public boolean backspaceCompare(String first, String second) {
      char[] firstChars = first.toCharArray();
      char[] secondChars = second.toCharArray();

      int firstSkip = 0;
      int secondSkip = 0;

      int firstIndex = firstChars.length - 1;
      int secondIndex = secondChars.length - 1;

      while (firstIndex >= 0 && secondIndex >= 0) {
        while (firstIndex >= 0) {
          if (firstChars[firstIndex] == '#') {
            firstSkip++;
            firstIndex--;
            continue;
          }

          if (firstSkip > 0) {
            firstIndex--;
            firstSkip--;
          } else {
            break;
          }
        }

        while (secondIndex >= 0) {
          if (secondChars[secondIndex] == '#') {
            secondSkip++;
            secondIndex--;
            continue;
          }

          if (secondSkip > 0) {
            secondIndex--;
            secondSkip--;
          } else {
            break;
          }
        }

        if (firstIndex >= 0 && secondIndex >= 0) {
          if (firstChars[firstIndex] == secondChars[secondIndex]) {
            firstIndex--;
            secondIndex--;
          } else {
            return false;
          }
        } else {
          break;
        }
      }

      while (firstIndex >= 0) {
        if (firstChars[firstIndex] == '#') {
          firstSkip++;
          firstIndex--;
          continue;
        }

        if (firstSkip > 0) {
          firstIndex--;
          firstSkip--;
          continue;
        }

        return false;
      }

      while (secondIndex >= 0) {
        if (secondChars[secondIndex] == '#') {
          secondSkip++;
          secondIndex--;
          continue;
        }

        if (secondSkip > 0) {
          secondIndex--;
          secondSkip--;
          continue;
        }

        return false;
      }

      return true;
    }
  }
}