62 行对还是64行对
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #define MAX_COLS 20
5 #define MAX_INPUT 1000
6
7 int read_column_numbers( int columns[], int max );
8 void rearrange( char *output, char const *input,
9 int n_columns, int const columns[] );
10
11 int main( void )
12 {
13 int n_columns;
14 int columns[MAX_COLS];
15 char input[MAX_INPUT];
16 char output[MAX_INPUT];
17
18 n_columns = read_column_numbers( columns, MAX_COLS );
19 while( gets(input) != NULL){
20 printf("Original input : %s\n", input);
21 rearrange( output, input, n_columns, columns );
22 printf("Rearranged line: %s\n", output);
23 }
24
25 return EXIT_SUCCESS;
26 }
27
28 int read_column_numbers( int columns[], int max)
29 {
30 int num = 0;
31 int ch;
32
33 while( num < max && scanf( "%d", &columns[num]) == 1 && columns[num] >= 0)
34 num += 1;
35 if( num % 2 != 0){
36 puts( "Last column number is not paired." );
37 exit( EXIT_FAILURE );
38 }
39
40 while ( (ch = getchar()) != EOF && ch != '\n' )
41 ;
42
43 return num;
44 }
45
46 void rearrange( char *output, char const *input, int n_columns, int const columns[] )
47 {
48 int col;
49 int output_col;
50 int len;
51
52 len = strlen( input );
53 output_col = 0;
54
55 for (col = 0; col < n_columns; col += 2)
56 {
57 int nchars = columns[col + 1] - columns[col] + 1;
58
59 if (columns[col] >= len || output_col == MAX_INPUT - 1)
60 break;
61 if (output_col + nchars > MAX_INPUT - 1)
62 nchars = MAX_INPUT - output_col;
63 // Or this
64 // nchars = MAX_INPUT - output_col - 1;
65 strncpy( output + output_col, input + columns[col], nchars );
66 output_col += nchars;
67 }
68 output[output_col] = '\0';
69 }
