使 for 循环继续，直到完成目标答案

【问题标题】：Make for loop continue until a goal is accomplished使 for 循环继续，直到完成目标
【发布时间】：2017-10-13 08:07:53
【问题描述】：

我需要能够找到 EEPROM 存储器的 5 个连续位，理想情况下最接近 2（因为我有与其他数据相关联的位 #1 和 2，并希望保持井井有条）。我开发了这段代码，它可以工作，但 for 循环在找到一组好的数字后继续。

Serial.println("got to assignment number finder");
for (int AssignCheck = 2; AssignCheck < 250; AssignCheck++){
  Serial.println("Finding a good assignment number " + String(AssignCheck));
  if (EEPROM.read(AssignCheck) == 255){          //Looks for a blank space which can be used to store the new card
    if (EEPROM.read(AssignCheck + 1) == 255){
      if (EEPROM.read(AssignCheck + 2) == 255){
        if (EEPROM.read(AssignCheck + 3) == 255){
          if (EEPROM.read(AssignCheck + 4) == 255){
            Serial.println("Found assignment numbers " + String(AssignCheck) + " through to " + String(int(AssignCheck) + 4) + ".  Scanner value = " + String(Scanner));
            int StoreValue = AssignCheck;
          }
        }
      }
    }
  }
}

然后我想我可以在它周围放一个 while 循环，一旦变量设置为 0 而不是 1，就让 while 循环停止，所以我写了这个：（注意 while 循环的引入，变量和中间的Scanner = 0 行）。

Serial.println("got to assignment number finder");
int Scanner = 1;
while (Scanner == 1){
  for (int AssignCheck = 2; AssignCheck < 250; AssignCheck++){
    Serial.println("Finding a good assignment number " + String(AssignCheck) + ".  Scanner value = " + String(Scanner));
    if (EEPROM.read(AssignCheck) == 255){          //Looks for a blank space which can be used to store the new card
      if (EEPROM.read(AssignCheck + 1) == 255){
        if (EEPROM.read(AssignCheck + 2) == 255){
          if (EEPROM.read(AssignCheck + 3) == 255){
            if (EEPROM.read(AssignCheck + 4) == 255){
              Scanner = 0;
              Serial.println("Found assignment numbers " + String(AssignCheck) + " through to " + String(int(AssignCheck) + 4) + ".  Scanner value = " + String(Scanner));
              int StoreValue = AssignCheck;
            }
          }
        }
      }
    }
  }
}

它在我需要时正确识别并将变量设置为 0，但 while 循环似乎没有影响，并且循环继续产生可以工作的数字集。

作为一名新手编码员，我不确定接下来可以尝试什么。

任何建议将不胜感激。

【问题讨论】：

只需在最后一个if 中添加一个break;？
或者如果你需要 while 来做别的事情，在 for 循环的条件中添加第二个中断条件的检查
如何编写正确的 C 代码：使用 5 个嵌套的 if 语句而不是循环。另外，为什么 5 个未编程的 eeprom 单元是理想的结果？这没有任何意义。 XY 问题。

标签： loops for-loop while-loop arduino

【解决方案1】：

在这种情况下，您可以使用指令break：

Serial.println("got to assignment number finder");
for (int AssignCheck = 2; AssignCheck < 250; AssignCheck++){
  Serial.println("Finding a good assignment number " + String(AssignCheck));
  if (EEPROM.read(AssignCheck) == 255){          //Looks for a blank space which can be used to store the new card
    if (EEPROM.read(AssignCheck + 1) == 255){
      if (EEPROM.read(AssignCheck + 2) == 255){
        if (EEPROM.read(AssignCheck + 3) == 255){
          if (EEPROM.read(AssignCheck + 4) == 255){
            Serial.println("Found assignment numbers " + String(AssignCheck) + " through to " + String(int(AssignCheck) + 4) + ".  Scanner value = " + String(Scanner));
            int StoreValue = AssignCheck;
            break;
          }
        }
      }
    }
  }
}

您可以阅读here，它完全符合您的要求。

请注意，您的第二次尝试不起作用，因为 for loop 在 while 内：它在整个 for loop 之前完成，然后比较while loop

你可以这样改：

Serial.println("got to assignment number finder");
int Scanner = 1;
for (int AssignCheck = 2; (AssignCheck < 250) && (Scanner == 1); AssignCheck++){
  Serial.println("Finding a good assignment number " + String(AssignCheck) + ".  Scanner value = " + String(Scanner));
  if (EEPROM.read(AssignCheck) == 255){          //Looks for a blank space which can be used to store the new card
    if (EEPROM.read(AssignCheck + 1) == 255){
      if (EEPROM.read(AssignCheck + 2) == 255){
        if (EEPROM.read(AssignCheck + 3) == 255){
          if (EEPROM.read(AssignCheck + 4) == 255){
            Scanner = 0;
            Serial.println("Found assignment numbers " + String(AssignCheck) + " through to " + String(int(AssignCheck) + 4) + ".  Scanner value = " + String(Scanner));
            int StoreValue = AssignCheck;
          }
        }
      }
    }
  }
}

【讨论】：

【解决方案2】：

读取 EEPROM 很贵，请考虑这个：

Serial.println("got to assignment number finder");
int Scanner = 1;
char rollingBuffer[5];
rollingBuffer[0] = EEPROM.read(2 + 0);
rollingBuffer[1] = EEPROM.read(2 + 1);
rollingBuffer[2] = EEPROM.read(2 + 2);
rollingBuffer[3] = EEPROM.read(2 + 3);
rollingBuffer[4] = EEPROM.read(2 + 4);
pointRoll = 0;
for (int AssignCheck = 7; (AssignCheck < 255); AssignCheck++)
{
    if ((rollingBuffer[0] == 255) && (rollingBuffer[1] == 255) && (rollingBuffer[2] == 255) && (rollingBuffer[3] == 255) && (rollingBuffer[4] == 255))
    {
        Serial.println("Found assignment numbers " + String(AssignCheck-5) + " through to " + String(int(AssignCheck-1)) + ".  Scanner value = " + String(Scanner));
        int StoreValue = AssignCheck;
        break;
    }
    rollingBuffer[pointRoll] = EEPROM.read(AssignCheck);
    pointRoll++;
    if (pointRoll > 4) pointRoll = 0;
}

【讨论】：

“读取 EEPROM 很昂贵” 那么如果算法不需要读取 5 次，为什么还要读取呢？