如何初始化“分钟"?变量正确吗? [英] how to initialize the "min" variable properly?

问题描述

我的代码中有一个小问题，无法从一系列数字中找到最小值.当我初始化min = 0时，最小值变为0.但是当我不初始化min时，答案是正确的！

I have a small problem in my code for finding the minimum value from a series of numbers. When I initialize min = 0, the minimum value turns out as 0. But when I don't initialize min, the answer is correct!

为什么会这样? Xcode告诉我应该初始化min变量.

Why does this happen? Xcode tells me I should initialize the min variable.

int a[20] = {0};
int max = 0;
int min ;
int sum = 0;

srand((unsigned)time(NULL));

for (int i = 1; i <= 20; i++) {
    a[i] = 100 + rand()%(200 - 100 + 1);

    if (max < a[i]) {
        max = a[i];
    }
    printf("%d,%d\n",a[i],i);

    if (min > a[i]) {
        min = a[i];
    }

    sum += a[i];
}

printf("最大值：%d\n",max);
printf("最小值：%d\n",min);
printf("平均值：%d\n",sum / 20);

推荐答案

编译器警告是因为访问未初始化变量的值会带来未定义的行为.

The compiler warning is because accessing the value of uninitialised variables gives undefined behaviour.

在数组中查找最小值的常用技术是将min初始化为数组中的第一个元素，然后遍历后续元素

A common technique to find a minimum value in an array is to initialise the min to be the first element in the array, then iterate over subsequent elements

 min = a[0];
 for (i = 1; i < 20; ++i)     /* assume 20 elements */
     if (a[i] < min) min = a[i];

这适用于可以使用<运算符进行比较的所有数字类型，而不必费力尝试查找超出数组中所有可能值的值.

This works for all numeric types that can be compared using the < operator, without having to muck around trying to find a value that exceeds all possible values in the array.

要注意的另一件事是数组索引从零开始.因此，包含20个元素的数组(如int a[20]中所示)具有有效的索引0至19.运行从1到20的循环-因此访问a[1]到a[20]会产生不确定的行为，因为a[20]不存在.

The other thing to watch is that array indexing starts at zero. So an array with 20 elements (as in int a[20]) has valid indices 0 to 19. Running a loop from 1 to 20 - and therefore accessing a[1] through to a[20] gives undefined behaviour, since a[20] does not exist.

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