for (size_t i = _height - 1; i >= 0; i--)这段代码看起来没有什么问题，其实有一个大坑，是因为size_t是一种非负类型，它永远都不可能会小于0,所以循环停不下来。把size_t改成int就没问题了。

1. #include"utils.h"
   
2. #include<iostream>
   
3. using namespace std;
   
4. 
   
5. void calMinDis()
   
6. {
   
7. bool **_map = NULL;
   
8. int **_min_dis;
   
9. int _height = 100;
   
10. int _width = 200;
    
11. 
    
12. _map = new bool*[_height];
    
13. for (size_t i = 0; i < _height; i++)
    
14. {
    
15. _map[i] = new bool[_width];
    
16. }
    
17. 
    
18. printf("cal min dis.\n");
    
19. if (_map == NULL)
    
20. {
    
21. printf("map haven't init.\n");
    
22. return;
    
23. }
    
24. 
    
25. _min_dis = new int *[_height];
    
26. for (size_t i = 0; i < _height; i++)
    
27. {
    
28. _min_dis[i] = new int[_width];
    
29. }
    
30. int MAX_INT = 0xffffffff >> 1;
    
31. for (size_t i = 0; i < _height; i++)
    
32. {
    
33. for (size_t j = 0; j < _width; j++)
    
34. {
    
35. if (_map[i][j])
    
36. {
    
37. _min_dis[i][j] = MAX_INT;
    
38. }
    
39. else
    
40. {
    
41. _min_dis[i][j] = 0;
    
42. }
    
43. }
    
44. }
    
45. for (size_t i = 0; i < _height; i++)
    
46. {
    
47. for (size_t j = 0; j < _width; j++)
    
48. {
    
49. if (!_map[i][j])
    
50. {
    
51. continue;
    
52. }
    
53. if (i > 0 && _min_dis[i - 1][j] < _min_dis[i][j])
    
54. {
    
55. _min_dis[i][j] = _min_dis[i - 1][j] + 1;
    
56. }
    
57. if (j > 0 && _min_dis[i][j - 1] < _min_dis[i][j])
    
58. {
    
59. _min_dis[i][j] = _min_dis[i][j - 1] + 1;
    
60. }
    
61. }
    
62. }
    
63. printf("1\n");
    
64. for (size_t i = _height - 1; i >= 0; i--)
    
65. {
    
66. for (size_t j = _width - 1; j >= 0; j--)
    
67. {
    
68. printf("(%d,%d)\n",i,j);
    
69. if (!_map[i][j])
    
70. {
    
71. continue;
    
72. }
    
73. if (i + 1 < _height && _min_dis[i + 1][j] < _min_dis[i][j])
    
74. {
    
75. _min_dis[i][j] = _min_dis[i + 1][j] + 1;
    
76. }
    
77. if (j + 1 < _width && _min_dis[i][j + 1] < _min_dis[i][j])
    
78. {
    
79. _min_dis[i][j] = _min_dis[i][j + 1] + 1;
    
80. }
    
81. }
    
82. }
    
83. printf("finished cal min dis.\n");
    
84. }
    
85. 
    
86. int main(int argc, char const *argv[])
    
87. {
    
88. calMinDis();
    
89. return 0;
    
90. }
    

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for (size_t i = _height - 1; i >= 0; i--)这段代码看起来没有什么问题，其实有一个大坑，是因为size_t是一种非负类型，它永远都不可能会小于0,所以循环停不下来。把size_t改成int就没问题了。

1. #include"utils.h"
   
2. #include<iostream>
   
3. using namespace std;
   
4. 
   
5. void calMinDis()
   
6. {
   
7. bool **_map = NULL;
   
8. int **_min_dis;
   
9. int _height = 100;
   
10. int _width = 200;
    
11. 
    
12. _map = new bool*[_height];
    
13. for (size_t i = 0; i < _height; i++)
    
14. {
    
15. _map[i] = new bool[_width];
    
16. }
    
17. 
    
18. printf("cal min dis.\n");
    
19. if (_map == NULL)
    
20. {
    
21. printf("map haven't init.\n");
    
22. return;
    
23. }
    
24. 
    
25. _min_dis = new int *[_height];
    
26. for (size_t i = 0; i < _height; i++)
    
27. {
    
28. _min_dis[i] = new int[_width];
    
29. }
    
30. int MAX_INT = 0xffffffff >> 1;
    
31. for (size_t i = 0; i < _height; i++)
    
32. {
    
33. for (size_t j = 0; j < _width; j++)
    
34. {
    
35. if (_map[i][j])
    
36. {
    
37. _min_dis[i][j] = MAX_INT;
    
38. }
    
39. else
    
40. {
    
41. _min_dis[i][j] = 0;
    
42. }
    
43. }
    
44. }
    
45. for (size_t i = 0; i < _height; i++)
    
46. {
    
47. for (size_t j = 0; j < _width; j++)
    
48. {
    
49. if (!_map[i][j])
    
50. {
    
51. continue;
    
52. }
    
53. if (i > 0 && _min_dis[i - 1][j] < _min_dis[i][j])
    
54. {
    
55. _min_dis[i][j] = _min_dis[i - 1][j] + 1;
    
56. }
    
57. if (j > 0 && _min_dis[i][j - 1] < _min_dis[i][j])
    
58. {
    
59. _min_dis[i][j] = _min_dis[i][j - 1] + 1;
    
60. }
    
61. }
    
62. }
    
63. printf("1\n");
    
64. for (size_t i = _height - 1; i >= 0; i--)
    
65. {
    
66. for (size_t j = _width - 1; j >= 0; j--)
    
67. {
    
68. printf("(%d,%d)\n",i,j);
    
69. if (!_map[i][j])
    
70. {
    
71. continue;
    
72. }
    
73. if (i + 1 < _height && _min_dis[i + 1][j] < _min_dis[i][j])
    
74. {
    
75. _min_dis[i][j] = _min_dis[i + 1][j] + 1;
    
76. }
    
77. if (j + 1 < _width && _min_dis[i][j + 1] < _min_dis[i][j])
    
78. {
    
79. _min_dis[i][j] = _min_dis[i][j + 1] + 1;
    
80. }
    
81. }
    
82. }
    
83. printf("finished cal min dis.\n");
    
84. }
    
85. 
    
86. int main(int argc, char const *argv[])
    
87. {
    
88. calMinDis();
    
89. return 0;
    
90. }
    

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