如何從字符串中提取多個數字C

我有一個問題。如果我想在字符串中提取多個float號碼，我該怎麼辦？我知道有像strtof這樣的函數可以提取數字。問題是如果有多於字符串中存在一個數字？如何從字符串中提取多個數字C

我只想和我知道只有需要的東西是找到數字後指向下一個字符的指針。然後繼續搜索，直到它達到\n但是如何？

例：

想象我有一個關於一些城鎮的降雨量報告期間一年，我想每個鎮提取物降雨（當它到達了鎮\n報告已完成）。

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int main(int argc, char **argv) 
{ 
    char* data = "Rome:Jan 81.2,Feb 63.2,Mar 70.3,Apr 55.7,May 53.0,Jun 36.4,Jul 17.5,Aug 27.5,Sep 60.9,Oct 117.7,Nov 111.0,Dec 97.9\n" 
    "London:Jan 48.0,Feb 38.9,Mar 39.9,Apr 42.2,May 47.3,Jun 52.1,Jul 59.5,Aug 57.2,Sep 55.4,Oct 62.0,Nov 59.0,Dec 52.9\n" 
    "Paris:Jan 182.3,Feb 120.6,Mar 158.1,Apr 204.9,May 323.1,Jun 300.5,Jul 236.8,Aug 192.9,Sep 66.3,Oct 63.3,Nov 83.2,Dec 154.7\n" 
    "NY:Jan 108.7,Feb 101.8,Mar 131.9,Apr 93.5,May 98.8,Jun 93.6,Jul 102.2,Aug 131.8,Sep 92.0,Oct 82.3,Nov 107.8,Dec 94.2\n" 
    "Vancouver:Jan 145.7,Feb 121.4,Mar 102.3,Apr 69.2,May 55.8,Jun 47.1,Jul 31.3,Aug 37.0,Sep 59.6,Oct 116.3,Nov 154.6,Dec 171.5\n" 
    "Sydney:Jan 103.4,Feb 111.0,Mar 131.3,Apr 129.7,May 123.0,Jun 129.2,Jul 102.8,Aug 80.3,Sep 69.3,Oct 82.6,Nov 81.4,Dec 78.2\n" 
    "Bangkok:Jan 10.6,Feb 28.2,Mar 30.7,Apr 71.8,May 189.4,Jun 151.7,Jul 158.2,Aug 187.0,Sep 319.9,Oct 230.8,Nov 57.3,Dec 9.4\n" 
    "Tokyo:Jan 49.9,Feb 71.5,Mar 106.4,Apr 129.2,May 144.0,Jun 176.0,Jul 135.6,Aug 148.5,Sep 216.4,Oct 194.1,Nov 95.6,Dec 54.4\n" 
    "Beijing:Jan 3.9,Feb 4.7,Mar 8.2,Apr 18.4,May 33.0,Jun 78.1,Jul 224.3,Aug 170.0,Sep 58.4,Oct 18.0,Nov 9.3,Dec 2.7\n" 
    "Lima:Jan 1.2,Feb 0.9,Mar 0.7,Apr 0.4,May 0.6,Jun 1.8,Jul 4.4,Aug 3.1,Sep 3.3,Oct 1.7,Nov 0.5,Dec 0.7"; 
    const char* towns[14] = {"Rome", "London", "Paris", "NY", "Vancouver", "Sydney", "Bangkok", "Tokyo", 
          "Beijing", "Lima", "Montevideo", "Caracas", "Madrid", "Berlin"}; 
    size_t i = 0; 
    float nums[12]; 
    char *ch_ptr = strstr(data,towns[0]); //pointing to first character 
    const char *stop ="\n"; 
    while((ch_ptr++) != stop) 
     { 
      nums[i] = strtof(); ///How should I do it ???? 
      i++; 
      } 
    return 0; 
}

來源

2017-10-15 Lucky Luke

如果您閱讀[manpage for strtod]（http://man7.org/man/3/strtod.3.html），您會發現它有兩個參數，其中第二個參數用於繼續掃描輸入。（我建議''strtod''而不是'strtof'，因爲除非你有一個好的理由，否則你應該總是使用'double'，而不是'float'（如果你必須問什麼是一個好理由，你沒有一個） – rici

不相關的，但是你的'while'循環中的那個條件並沒有達到你想象的那樣 –

@JimLewis我只是想知道只有在找到數字後才需要指向下一個字符的指針。然後繼續搜索，直到它到達'\ n' –

使用兩個嵌套for循環，可以捕獲每個城鎮和月份的浮點值。

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int main(int argc, char **argv) 
{ 


    char* data = "Rome:Jan 81.2,Feb 63.2,Mar 70.3,Apr 55.7,May 53.0,Jun 36.4,Jul 17.5,Aug 27.5,Sep 60.9,Oct 117.7,Nov 111.0,Dec 97.9\n" 
    "London:Jan 48.0,Feb 38.9,Mar 39.9,Apr 42.2,May 47.3,Jun 52.1,Jul 59.5,Aug 57.2,Sep 55.4,Oct 62.0,Nov 59.0,Dec 52.9\n" 
    "Paris:Jan 182.3,Feb 120.6,Mar 158.1,Apr 204.9,May 323.1,Jun 300.5,Jul 236.8,Aug 192.9,Sep 66.3,Oct 63.3,Nov 83.2,Dec 154.7\n" 
    "NY:Jan 108.7,Feb 101.8,Mar 131.9,Apr 93.5,May 98.8,Jun 93.6,Jul 102.2,Aug 131.8,Sep 92.0,Oct 82.3,Nov 107.8,Dec 94.2\n" 
    "Vancouver:Jan 145.7,Feb 121.4,Mar 102.3,Apr 69.2,May 55.8,Jun 47.1,Jul 31.3,Aug 37.0,Sep 59.6,Oct 116.3,Nov 154.6,Dec 171.5\n" 
    "Sydney:Jan 103.4,Feb 111.0,Mar 131.3,Apr 129.7,May 123.0,Jun 129.2,Jul 102.8,Aug 80.3,Sep 69.3,Oct 82.6,Nov 81.4,Dec 78.2\n" 
    "Bangkok:Jan 10.6,Feb 28.2,Mar 30.7,Apr 71.8,May 189.4,Jun 151.7,Jul 158.2,Aug 187.0,Sep 319.9,Oct 230.8,Nov 57.3,Dec 9.4\n" 
    "Tokyo:Jan 49.9,Feb 71.5,Mar 106.4,Apr 129.2,May 144.0,Jun 176.0,Jul 135.6,Aug 148.5,Sep 216.4,Oct 194.1,Nov 95.6,Dec 54.4\n" 
    "Beijing:Jan 3.9,Feb 4.7,Mar 8.2,Apr 18.4,May 33.0,Jun 78.1,Jul 224.3,Aug 170.0,Sep 58.4,Oct 18.0,Nov 9.3,Dec 2.7\n" 
    "Lima:Jan 1.2,Feb 0.9,Mar 0.7,Apr 0.4,May 0.6,Jun 1.8,Jul 4.4,Aug 3.1,Sep 3.3,Oct 1.7,Nov 0.5,Dec 0.7"; 
    const char* months[12] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun" 
    , "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; 
    const char* towns[14] = {"Rome", "London", "Paris", "NY", "Vancouver", "Sydney", "Bangkok", "Tokyo", 
    "Beijing", "Lima", "Montevideo", "Caracas", "Madrid", "Berlin"}; 
    size_t i = 0; 
    float nums[12]; 
    char *end = NULL; 
    char *town_ptr = NULL; 
    char *month_ptr = NULL; 
    char monthid[100] = ""; 
    char townid[100] = ""; 
    for (int town = 0; town < 14; town++) 
    { 
     if ((town_ptr = strstr (data, towns[town]))) { 
      i = 0; 
      sscanf (town_ptr, "%99[^:]", townid); 
      for (int month = 0; month < 12; month++) 
      { 
       if ((month_ptr = strstr (town_ptr, months[month]))) { 
        sscanf (month_ptr, "%99s", monthid); 
        month_ptr += strlen (months[month]); 
        nums[i] = strtof(month_ptr, &end); 
        if (*end == ',' || *end == '\n' || *end == '\0') { 
         printf ("%s %s nums[%d] = %f\n", townid, monthid, i, nums[i]); 
         i++; 
        } 
       } 
      } 
     } 
    } 
    return 0; 
}

將城鎮名稱解析爲換行符。如果一個城鎮失去了一個月，則以前的代碼將使用來自下一個城鎮的月份。這將從鎮名重複，直到十二個值，一個換行符，一個'\0'或未能解析一個double。

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int main(int argc, char **argv) 
{ 


    char* data = "Rome:Jan 81.2,Feb 63.2,Mar 70.3,Apr 55.7,May 53.0,Jun 36.4,Jul 17.5,Aug 27.5,Sep 60.9,Oct 117.7,Nov 111.0,Dec 97.9\n" 
    "London:Jan 48.0,Feb 38.9,Mar 39.9,Apr 42.2,May 47.3,Jun 52.1,Jul 59.5,Aug 57.2,Sep 55.4,Oct 62.0,Nov 59.0,Dec 52.9\n" 
    "Paris:Jan 182.3,Feb 120.6,Mar 158.1,Apr 204.9,May 323.1,Jun 300.5,Jul 236.8,Aug 192.9,Sep 66.3,Oct 63.3,Nov 83.2,Dec 154.7\n" 
    "NY:Jan 108.7,Feb 101.8,Mar 131.9,Apr 93.5,May 98.8,Jun 93.6,Jul 102.2,Aug 131.8,Sep 92.0,Oct 82.3,Nov 107.8,Dec 94.2\n" 
    "Vancouver:Jan 145.7,Feb 121.4,Mar 102.3,Apr 69.2,May 55.8,Jun 47.1,Jul 31.3,Aug 37.0,Sep 59.6,Oct 116.3,Nov 154.6,Dec 171.5\n" 
    "Sydney:Jan 103.4,Feb 111.0,Mar 131.3,Apr 129.7,May 123.0,Jun 129.2,Jul 102.8,Aug 80.3,Sep 69.3,Oct 82.6,Nov 81.4,Dec 78.2\n" 
    "Bangkok:Jan 10.6,Feb 28.2,Mar 30.7,Apr 71.8,May 189.4,Jun 151.7,Jul 158.2,Aug 187.0,Sep 319.9,Oct 230.8,Nov 57.3,Dec 9.4\n" 
    "Tokyo:Jan 49.9,Feb 71.5,Mar 106.4,Apr 129.2,May 144.0,Jun 176.0,Jul 135.6,Aug 148.5,Sep 216.4,Oct 194.1,Nov 95.6,Dec 54.4\n" 
    "Beijing:Jan 3.9,Feb 4.7,Mar 8.2,Apr 18.4,May 33.0,Jun 78.1,Jul 224.3,Aug 170.0,Sep 58.4,Oct 18.0,Nov 9.3,Dec 2.7\n" 
    "Lima:Jan 1.2,Feb 0.9,Mar 0.7,Apr 0.4,May 0.6,Jun 1.8,Jul 4.4,Aug 3.1,Sep 3.3,Oct 1.7,Nov 0.5,Dec 0.7"; 
    const char* towns[14] = {"Rome", "London", "Paris", "NY", "Vancouver", "Sydney", "Bangkok", "Tokyo", 
    "Beijing", "Lima", "Montevideo", "Caracas", "Madrid", "Berlin"}; 
    float nums[12]; 
    char *end = NULL; 
    char *town_ptr = NULL; 
    char monthid[100] = ""; 
    char townid[100] = ""; 
    int span = 0; 
    for (int town = 0; town < 14; town++) 
    { 
     if ((town_ptr = strstr (data, towns[town]))) {//find the town name 
      sscanf (town_ptr, "%99[^:]:%n", townid, &span); 
      int each = 0; 
      town_ptr += span; 
      do { 
       sscanf (town_ptr, "%s%n", monthid, &span); 
       town_ptr += span; 
       nums[each] = strtod (town_ptr, &end); 
       if (end == town_ptr) {//failed to parse a double 
        break; 
       } 
       printf ("%s %s nums[%d] = %f\n", townid, monthid, each, nums[each]); 
       town_ptr = end + 1;//to advance past the comma 
       each++; 
      } while (each < 12 && *end != '\0' && *end != '\n'); 
     } 
    } 
    return 0; 
}

來源

2017-10-15 18:58:48 xing

如何從字符串中提取多個數字C

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