英文:
Why for loop doesn't work for 2D array with an overflow but still works for 1D array
问题
以下是翻译好的部分：
"The for loop to store values to two 1D arrays can store and print values even with an overflow but why a program to store values to 2D array using for loop doesn't run when there is an overflow?"
"用for循环将值存储到两个一维数组中，即使溢出，也可以存储和打印值，但为什么使用for循环将值存储到二维数组的程序在溢出时不运行？"
"The following program runs:"
"以下程序可以运行："
#include <stdio.h>int main(){int i, a[5], b[6];for (i = 0; i <= 6; i++){a[i] = i;b[i] = i;}for (i = 0; i <= 6; i++){printf(" %d", a[i], b[i]);}return 0;}
"But why the following program doesn't run?"
"但为什么以下程序不运行？"
#include <stdio.h>int main(){int i, j, a[5][5];for (i = 0; i <= 5; i++){for (j = 0; j <= 5; j++){a[i][j] = j;}}for (i = 0; i <= 5; i++){for (j = 0; j <= 5; j++){printf(" %d", a[i][j]);}printf("\n");}return 0;}
"I tried to store the values in 2D array using nested for loop but it doesn't run. However, the program runs when 1D array is used."
"我尝试使用嵌套的for循环将值存储在二维数组中，但它不运行。然而，当使用一维数组时，程序可以运行。"
英文:
The for loop to store values to two 1D arrays can store and print values even with an overflow but why a program to store values to 2D array using for loop doesn't run when there is an overflow?
The following program runs:
#include <stdio.h>int main(){int i, a[5], b[6];for (i = 0; i <= 6; i++){a[i] = i;b[i] = i;}for (i = 0; i <= 6; i++){printf(" %d", a[i], b[i]);}return 0;}
But why the following program doesn't run?
#include <stdio.h>int main(){int i, j, a[5][5];for (i = 0; i <= 5; i++){for (j = 0; j <= 5; j++){a[i][j] = j;}}for (i = 0; i <= 5; i++){for (j = 0; j <= 5; j++){printf(" %d", a[i][j]);}printf("\n");}return 0;}
I tried to store the values in 2D array using nested for loop but it doesn't run. However, the program runs when 1D array is used.
答案1
得分: 0
第一个你分享的代码有效，因为你很幸运。当你说 int a[5] 时，这意味着你分配了 5 个整数单元，从零到四开始。不包括五。
修正后的第一个代码：
#include <stdio.h>int main(){int i, a[5], b[6];for (i = 0; i <= 4; i++){a[i] = i;}for (i = 0; i <= 5; i++){b[i] = i;}for (i = 0; i <= 5; i++){if(i<5)printf("a= %d\nb= %d", a[i], b[i]);elseprintf("b=%d",b[i]);}return 0;}
对于第二个代码，同样不应该尝试使用边界。
修正后的第二个代码：
#include <stdio.h>int main(){int i, j, a[5][5];for (i = 0; i < 5; i++){for (j = 0; j < 5; j++){a[i][j] = j;}}for (i = 0; i < 5; i++){for (j = 0; j < 5; j++){printf(" %d", a[i][j]);}printf("\n");}return 0;}
英文:
First one that you shared works because you are lucky. When you say
int a[5] this means you allocated 5 unit for integer and it starts from zero to four. It does not include five.
Fixed code first one:
#include <stdio.h>int main(){int i, a[5], b[6];for (i = 0; i <= 4; i++){a[i] = i;}for (i = 0; i <= 5; i++){b[i] = i;}for (i = 0; i <= 5; i++){if(i<5)printf("a= %d\nb= %d", a[i], b[i]);elseprintf("b=%d",b[i]);}return 0;}
for the second again you shouldn't try to use boundaries
Fixed code:
#include <stdio.h>int main(){int i, j, a[5][5];for (i = 0; i < 5; i++){for (j = 0; j < 5; j++){a[i][j] = j;}}for (i = 0; i < 5; i++){for (j = 0; j < 5; j++){printf(" %d", a[i][j]);}printf("\n");}return 0;}
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