如何通过C中的stdin从用户输入中打印最大数字 [英] How to print largest number from a user input through stdin in C.

问题描述

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define BUFFER_SIZE 150 /*maximum allowed characters*/

int main(int argc, char *a[])
{
    char *buff = malloc(BUFFER_SIZE);
    if(!buff)
    {
        return -1;
    }

    /*Standard Input*/
    int read = fgets(buff,BUFFER_SIZE,stdin);
    if(-1 != read)
    {
        char *word;
        char *ptr = buff;
        int max = NULL;

        while(word = strtok(ptr,"\t\n"))
        {
            int i = *word % 10;
            if(i>=0 && i <=9)
            {
                if(*word > max)
                {
                    max = *word;
                }
            }
            ptr = NULL;
        }
        /*Standard Output*/
        printf("Output:%d\n",max);
    }
    else
    {
        printf("No input string\n");
        return -1;
    }
    free(buff);
    buff= NULL;
    return 0;
}

我尝试过：



通过c中的stdin从用户输入打印最大数字。

输入字符串10 abc 20 abc 30 4。

输出应为30，但程序返回49.

What I have tried:

Print largest number from a user input through stdin in c.
Input string "10 abc 20 abc 30 4".
The output should be 30, but program is returning 49.

推荐答案

我担心 ptr = NULL; 过早结束循环。

oops，关于 C库函数 - strtok（） [ ^ ]具有误导性。

从您的输入样本中，我认为空格应该是分隔符。

当令牌是数字时，您需要转换它整数。

使用调试器检查你的代码是否符合预期。



有一个工具可以让你看到什么你的代码正在做，它的名字是调试器。它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪种期望与现实相符。

当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。

使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量。



调试器 - 维基百科，免费的百科全书 [ ^ ]



掌握Visual Studio 2010中的调试 - 初学者指南 [ ^ ]

使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]

调试器在这里向您展示您的代码正在做什么，您的任务是与什么进行比较应该这样做。

调试器中没有魔法，它没有找到错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。

I fear ptr = NULL; is ending the loop too soon.
oops, the explanation on C library function - strtok()[^] was misleading.
From your input sample, I think space should be in delimiters.
When the token is a number, you need to convert it to integer.
Use the debugger to check that your code do what you expect.

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

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