c - 段错误(核心转储)错误，在 C 搜索函数中

Question

我正在尝试编写一个 C 程序来获取离散正整数数组并找到最长递增子序列的长度。

'int* a'是随机生成的整数数组，长度为'int b'

调用:lis_n = answer(seq, seq_size);

功能:

int answer(int* a, int b) {
    if (a == NULL) {return -1;}
    int i = 0;
    int j = 0;
    int k = 0;
    //instantiate max and set it to 0
    int max = 0;
    //make an array storing all included numbers
    int included[b];
    memset(included, 0, b*sizeof(int));
    //create a pointer to the index in included[] with the largest value
    int indexMax = 0;
    //create a pointer to the index in a[]
    int indexArray = 0;
    //index of a[] for max included
    int maxToA = 0;
    //set the first included number to the first element in a[]
    included[indexMax] = a[indexArray];
    //loop until break
    while (1) {
        if (a[indexArray] > included[indexMax]/*digit greater than last included*/) {
            //include the digit
            included[indexMax+1] = a[indexArray];
            //increment current max pointer
            indexMax++;
        }
        j = b - 1;
        while (indexArray >= j/*pointer is at end"*/) {
            if (j == (b - 1)) {
                if ((indexMax+1) > max/*total is greater than current max*/) {
                    max = indexMax + 1;
                }
            }
            if (a[b-1] == included[0]/*last element is in included[0], stop*/) {
                return max;
            } else {
                //max included is set to zero
                included[indexMax] = 0;
                //max included pointer decreased
                indexMax--;
                //set array pointer to new max included
                for (k=0;k<(b-1);k++) {
                    if (a[k] == included[indexMax]) {
                        indexArray = k;
                    }
                }
                //increment array pointer
                indexArray++;
                j--;
            }
        }
        indexArray++;

        printf("(");
        for (i=0;i<b;i++) {
            printf("%d,",included[i]);
        }
        printf(")");
    }
}

我在运行时在终端中收到“段错误(核心已转储)”。

任何帮助都会很棒。

Answer 1

你已经声明了

int indexMax = 0;

这里你用它作为数组索引

incuded[indexMax] = 0;

递增和递减

indexMax++;
...
indexMax--;

你检查它的范围但你不限制它，你改变你与之比较的值

if ((indexMax+1) > max/*total is greater than current max*/) {
                max = indexMax + 1;
}

你永远不会检查 indexMax 与 b 或 0

int included[b];

所以你几乎可以肯定会超出 included[] 的范围。

一些一般性的建议。让你的函数和变量名有意义。尽可能避免过早退出函数。尽可能避免 while(1)。并且从不对数组大小(包括 C“字符串”)做出假设。投入管理费用似乎很辛苦，但这是有返回的。返回不仅仅是捕获意外错误，它让您在编写代码时思考您正在编写的代码。