无限while循环随机数

问题描述

我有这个代码：

  void generar（）{
 
 while（true）{ 
 if（yPos == topOfTheWorld）{
 scene [xPos] [yPos] = 2; 
} else if（yPos> = topOfTheWorld）{
 scene [xPos] [yPos] = 1; 
} else if（yPos< topOfTheWorld）{
 scene [xPos] [yPos] = 0; 
} else {
 scene [xPos] [yPos] = 0; 
} 
 
 yPos ++; 
 
 if（yPos> worldHeight）{
 topOfTheWorld + = 0; 
 yPos = 0; 
 xPos ++; 
} 
 
 if（xPos> worldWidth）{
 break; 
} 
} 
 
 std :: ofstream output（mapa.txt）; 
 for（int y = 0; y< worldHeight; y ++）{
 for（int x = 0; x  output<< scene [x] [y ]; 
 
 if（x } < std :: endl;} 
} 
 
 MessageBox（0，World generation has finished！，Finished！，MB_OK） 
 
} 
  

生成一个基于数组的世界。但是当我添加：

  slope = random（5） 
  

To：

 code> if（yPos == worldHeight）{
 topOfTheWorld + = 0; //将有斜率变量... 
 
 if（yPos == worldHeight）{
 slope = random（5）-2; 
 topOfTheWorld + = slope; 
  

由于某种原因， while

（随机函数）

  #include< time.h> 
 #include< windows.h> 
 
 int random（int n = 0）{
 
 srand（time（NULL））; 
 
 if（n！= 0）{
 return rand（）％n; 
} else {
 return rand（） 
} 
 
} 
  

（变量）

  const int worldWidth = 50; 
 const int worldHeight = 26; 
 int topOfTheWorld = worldHeight / 2; 
 int xPos = 0; 
 int yPos = 0; 
 int scene [worldWidth] [worldHeight]; 
 int slope; 
  

我能做什么？

解决方案

您显示 scene 定义为：

  int scene [worldWidth] [worldHeight];但是，您的代码具有：
 
 
 <$> 
 
 
 p $ p>  if（xPos> worldWidth）{
 break; 
} 
  

这意味着你会在数组边界之外写一个值 xPos == worldWidth ，这会导致未定义的行为。添加 slope 变量可能会导致变量组织发生变化，导致未定义的行为会影响和/或所有循环控制变量的值。

要修复，您应该更改错误检查：

  if（xPos& = worldWidth）{
 break; 
} 
  

您已经使用代码编辑了您的问题， > yPos 以类似的方式检查不正确。

I have this code:

void generar() {

    while (true) {
        if (yPos == topOfTheWorld) {
            scene[xPos][yPos] = 2;
        } else if (yPos >= topOfTheWorld) {
            scene[xPos][yPos] = 1;
        } else if(yPos < topOfTheWorld) {
            scene[xPos][yPos] = 0;
        } else {
            scene[xPos][yPos] = 0;
        }

        yPos++;

        if(yPos>worldHeight) {
            topOfTheWorld += 0;
            yPos = 0;
            xPos++;
        }

        if (xPos>worldWidth) {
                    break;
        }
    }

std::ofstream output("mapa.txt");
    for(int y=0;y<worldHeight;y++) {
        for(int x=0;x<worldWidth;x++) {
            output<<scene[x][y];

            if(x<(worldWidth-1)){output<<",";}
        }
        if(y<(worldHeight-1)){output<<std::endl;}
    }

MessageBox(0, "World generation has finished!", "Finished!", MB_OK);

}

That generates a world based in an array. But when I add:

slope = random(5)-2;

To:

if(yPos == worldHeight) {
    topOfTheWorld += 0; //There would be the slope var...

if(yPos == worldHeight) {
    slope = random(5)-2;
    topOfTheWorld += slope;

For some reason the while becomes an infinite loop, and I don't know why.

(Random Function)

#include <time.h>
#include <windows.h>

int random(int n = 0) {

srand(time(NULL));

if(n!=0){
return rand() % n;
} else {
return rand();
}

}

(Variables)

const int worldWidth = 50;
const int worldHeight = 26;
int topOfTheWorld = worldHeight/2;
int xPos = 0;
int yPos = 0;
int scene[worldWidth][worldHeight];
int slope;

What can I do?

解决方案

You show that scene is defined as:

int scene[worldWidth][worldHeight];

However, your code has this:

        if (xPos>worldWidth) {
                    break;
        }

Which means you will actually write a value outside the array boundary when xPos == worldWidth, and this causes undefined behavior. Adding the slope variable may cause your variable organization to change in a way that the undefined behavior ends up affecting the values of and or all of your loop control variables.

To fix, you should change the erroneous check with:

        if (xPos>=worldWidth) {
                    break;
        }

You have since edited your question with code that makes your yPos check incorrect in a similar way.

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