c - 在C中重复生成相同值的随机字符串和数字

Question

这个问题已经有答案了:

srand() — why call it only once? (7 个回答)

已关闭 8 年前。

我正在尝试用 C 实现 AVL 树。我在每个节点存储一个随机整数和一个随机字符串。我更改了代码并获取了随机字符串。但现在我现在有另一个问题。在按序遍历期间，我得到与输出相同的字符串。

有人可以检查我的代码吗？

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

time_t t;

struct node {
    int val;
    char *str;
    struct node *left_child;
    struct node *right_child;
};

struct node* LL_rotation(struct node *root) {
    struct node *children;
    children = root -> left_child;
    root -> left_child = children -> right_child;
    children -> right_child = root;
    return children;
}

struct node* RR_rotation(struct node *root) {
    struct node *children;
    children = root -> right_child;
    root -> right_child = children -> left_child;
    children -> left_child = root;
    return children;
}

struct node* LR_rotation(struct node *root) {
    struct node *children;
    children = root -> left_child;
    root -> left_child = RR_rotation(children);
    return LL_rotation(root);
}

struct node* RL_rotation(struct node *root) {
    struct node *children;
    children = root -> right_child;
    root -> right_child = LL_rotation(children);
    return RR_rotation(root);
}

int height(struct node *target) {
    int h = 0, lh, rh, maxh;
    if (target != NULL) {
        lh = height(target -> left_child);
        rh = height(target -> right_child);
        if (rh > lh) {
            maxh = rh;
        } else {
            maxh = lh;
        }
        h = maxh + 1;
    }
    return h;
}

int height_difference(struct node *target) {
    int lh, rh, b;
    lh = height(target -> left_child);
    rh = height(target -> right_child);
    b = lh - rh;
    return b;
}

struct node* decide_rotation(struct node *target) {
    int diff = height_difference(target);
    int res;
    if (diff > 1) {
        res = height_difference(target -> left_child);
        if (res > 0) {
            target = LL_rotation(target);
        } else {
            target = LR_rotation(target);
        }
    } else if (diff < -1) {
        res = height_difference(target -> right_child);
        if (res > 0) {
            target = RL_rotation(target);
        } else {
            target = RR_rotation(target);
        }
    }
    return target;
}

struct node* insert(struct node *target, int data, char *info) {
    if (target == NULL) {
        target = (struct node*) malloc(sizeof(struct node));
        target -> val = data;
        target -> str = info;
        target -> left_child = NULL;
        target -> right_child = NULL;
        return target;
    } else if (data > target -> val) {
        target -> right_child = insert(target -> right_child, data, info);
        target = decide_rotation(target);
    } else if (data < target -> val) {
        target -> left_child = insert(target -> left_child, data, info);
        target = decide_rotation(target);
    }
    return target;
}

void ioTraverse(struct node *tree) {//in-order traversal
    if (tree == NULL) {
        return;
    } else {
        ioTraverse(tree -> left_child);
        printf("%d %s\n", tree -> val, tree -> str);
        ioTraverse(tree -> right_child);
    }
}

void random_string_generator(char foo[], int length) {
    int i = 0;
    length--;
    while (length--) {
        foo[i] = rand() % 94 + 33;
        i++;
    }
    return;
}

int rand_range(int min, int max) {
    return rand() % (max - min + 1) + min;
}

int main() {
    srand(0);
    printf("Enter the no. of elements:\n");
    int n, ch, i, val, idx = 1;
    scanf("%d", &n);
    struct node *tree = NULL;
    for (i = 0; i < n; i++) {
        char res[123];
        random_string_generator(res, 6);
        printf("%s\n", res);
    }
    for (i = 0; i < n; i++) {
        char foo[123];
        val = rand_range(idx, idx + 100);
        //scanf("%d", &val);
        random_string_generator(foo, 6);
        //scanf("%s", &foo);
        printf("%s\n", foo);
        tree = insert(tree, val, foo);
        idx += rand_range(200, rand_range(240, 260));
        //ioTraverse(tree);
    }
    ioTraverse(tree);
    return 0;
}

Answer 1

我认为这与传递给 srand() 方法的种子有关。

time() 方法返回当前时间(以秒为单位)，因此在程序执行过程中，time(0) + getpid() 始终保持不变，因此会生成相同的整数在 rand() 函数中。