Program 1.1 rearrange. c, 1.1rearrange.c

Program 1.1 rearrange. c, 1.1rearrange.c

1/* 2 ** this program reads the input line from the standard input (keyboard) and processes it as needed and prints it in the standard output (screen, 3 ** the next line of each input row is the output content of the row processed as needed. 4 ** 5 ** the input 1st rows are a series of column numbers, ending with a negative number at the end of the string. 6 ** these column labels appear in pairs, indicating the columns of the input row to be printed. 7 ** for example, 0 3 10 12-1 indicates that columns 0th to 3rd are printed. 8 */9 10 # include <stdio. h> 11 # include <stdlib. h> 12 # include <string. h> 13 # maximum number of column labels processed by define MAX_COLS 20/*/14 # Maximum length of input rows processed by define MAX_INPUT 1000/*/15 16 int read_column_numbers (int columns [], int max); 17 void rearrange (char * output, char const * input, int n_columns, int const columns []); 18 19 int main (void) 20 {21 int n_columns; /* record Jun: Number of actually read Column labels */22 int columns [MAX_COLS];/* Capacity Ji Jun: Actually read Column numbers */23 char input [MAX_INPUT];/* container Jun: input line string */24 char output [MAX_INPUT];/* container Jun: output line string */25 26/* 27 ** read the column number of this string and calculate the number of 28 */29 n_columns = read_column_numbers (columns, MAX_COLS ); 30 31/* 32 ** read, process, and print the remaining input rows 33 */34 while (gets (input )! = NULL) 35 {36 printf ("original input: % s \ n", input); 37 rearrange (output, input, n_columns, columns); 38 printf ("truncated output: % s \ n ", output); 39} 40 41 return EXIT_SUCCESS; 42} 43 44/* 45 ** read Column label (saved to array), out of the specified range (2) the 46 ** 47 ** parameter table is ignored: columns column labels are stored with the array 48 ** max array maximum capacity 49 ** 50 ** returned value: num actually reads the number of column labels 51 */52 int read_column_numbers (int columns [], int max) 53 {54 int num = 0;/* count Jun: number of currently read Column numbers */55 int end_c H;/* record Jun: End character */56 57/* 58 ** Number of read columns, if the number of reads is less than 0, stop 59 */60 while (num <max & scanf ("% d", & columns [num]) = 1 & columns [num]> = 0) 61 {62 num + = 1; 63} 64 65/* 66 ** confirm that the read number is an even number, because they appear in the format of 67 */68 if (num % 2! = 0) 69 {70 puts ("Last column number is not supported Red. "); 71 exit (EXIT_FAILURE); 72} 73 74/* 75 ** discard the column number that exceeds the limit, prevent being interpreted as 1st rows of Data 76 */77 while (end_ch = getchar ())! = EOF & end_ch! = '\ N') 78; 79 80 return num; 81} 82 83/* 84 ** processes the input row and Concatenates the characters in the specified column, output rows end with NUL 85 */86 void rearrange (char * output, char const * input, int n_columns, int const columns []) 87 {88 int I; /* counting Jun: subscript of the columns array */89 int len;/* record Jun: length of the input row */90 int out_emp_ I;/* counting Jun: the subscript at the beginning of the output array space */91 92 len = strlen (input); 93 94 out_emp_ I = 0;/* bug: forgot to initialize */95 96/* 97 ** to process each pair of column numbers 98 */99 for (I = 0; I <n_columns; I ++ = 2) 100 {101 int nchars = columns [I + 1]-columns [I] + 1; /* number of characters written and output */102/103/* 104 ** if the input row ends or the output row array is full, end the task 105 */106 if (columns [I]> = len | out_emp_ I = MAX_INPUT-1) 107 {108 break; 109} 110 111/* 112 ** if the data space of the output row is insufficient, only 113 of the data that can be accommodated can be copied */114 if (out_emp_ I + nchars> MAX_INPUT-1) 115 {116 nchars = MAX_INPUT-1-out_emp_ I; 117} 118 119/* 120 ** copy related data (like pointer offset usage) 121 */122 strncpy (output + out_emp_ I, input + columns [I], nchars); 123 out_emp_ I + = nchars; 124} 125 output [out_emp_ I] = '\ 0 '; 126}