docs: 添加仓库地址到README；chore: 整理实验分析；feat: Kruskal最小生成树与图存储结构

exercise/24.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#ifdef _WIN32
+#include <windows.h>
+#include <direct.h>
+#endif
+
+// 栈结构定义
+typedef struct
+{
+    long long *data;
+    int top;
+    int capacity;
+} Stack;
+
+// 栈初始化
+void stack_init(Stack *st, int initial_capacity)
+{
+    int cap = initial_capacity > 0 ? initial_capacity : 2;
+
+    st->data = (long long *)malloc(sizeof(long long) * cap);
+    st->top = 0;
+    st->capacity = cap;
+}
+
+// 栈释放
+void stack_free(Stack *st)
+{
+    free(st->data);
+    st->data = NULL;
+    st->top = 0;
+    st->capacity = 0;
+}
+
+// 栈是否为空
+int stack_empty(const Stack *st)
+{
+    return st->top == 0;
+}
+
+// 栈压栈
+void stack_push(Stack *st, long long v)
+{
+    if (st->top >= st->capacity)
+    {
+        int new_cap = st->capacity ? st->capacity * 2 : 2;
+        long long *nd = (long long *)realloc(st->data, sizeof(long long) * new_cap);
+        if (!nd)
+        {
+            free(st->data);
+            exit(0);
+        }
+        st->data = nd;
+        st->capacity = new_cap;
+    }
+    st->data[st->top++] = v;
+}
+
+// 栈弹栈
+long long stack_pop(Stack *st)
+{
+    if (st->top == 0)
+    {
+        return 0;
+    }
+    return st->data[--st->top];
+}
+
+// 栈顶元素
+long long stack_top(const Stack *st)
+{
+    if (st->top == 0)
+    {
+        return 0;
+    }
+    return st->data[st->top - 1];
+}
+
+int main(void)
+{
+    // 设置控制台编码为UTF-8,防止中文乱码
+#ifdef _WIN32
+    system("chcp 65001 > nul"); // 设置控制台编码为UTF-8
+    SetConsoleOutputCP(65001);  // 设置控制台输出编码
+    SetConsoleCP(65001);        // 设置控制台输入编码
+#endif
+
+    // 动态读取一行表达式
+    size_t cap = 1024, len = 0;
+    char *s = (char *)malloc(cap);
+    if (!s)
+        return 0;
+    int ch;
+    // 读取表达式
+    while ((ch = getchar()) != EOF && ch != '\n')
+    {
+        if (len + 1 >= cap)
+        {
+            // 容量不足时，倍增扩容
+            cap <<= 1;
+            char *ns = (char *)realloc(s, cap);
+            if (!ns)
+            {
+                free(s);
+                return 0;
+            }
+            s = ns;
+        }
+        // 逐字符写入
+        s[len++] = (char)ch;
+    }
+    s[len] = '\0';
+    if (len == 0)
+    {
+        free(s);
+        return 0;
+    }
+
+    Stack st;
+    stack_init(&st, (int)len + 1);
+
+    long long num = 0;
+    // 记录最近的运算符，初始为加号
+    char op = '+';
+
+    for (size_t i = 0; i < len; ++i)
+    {
+        char c = s[i];
+        // 跳过空格字符
+        if (isspace((unsigned char)c))
+            continue;
+
+        if (isdigit((unsigned char)c))
+        {
+            // 累积多位数字
+            num = num * 10 + (c - '0');
+        }
+        else
+        {
+            // 根据“前一个”运算符 op 处理当前数字 num；
+            // 乘除即时计算以确保高于加减的优先级
+            switch (op)
+            {
+            case '+':
+                stack_push(&st, num);
+                break;
+            case '-':
+                stack_push(&st, -num);
+                break;
+            case '*':
+            {
+                long long a = stack_pop(&st);
+                stack_push(&st, a * num);
+                break;
+            }
+            case '/':
+            {
+                long long a = stack_pop(&st);
+                stack_push(&st, a / num);
+                break;
+            }
+            default:
+                break;
+            }
+            // 更新待应用的运算符为当前位置字符
+            op = c;
+            // 重置当前数字，继续解析
+            num = 0;
+        }
+    }
+
+    // 处理末尾累积数字（循环结束后最后一个数尚未被处理）
+    switch (op)
+    {
+    case '+':
+        stack_push(&st, num);
+        break;
+    case '-':
+        stack_push(&st, -num);
+        break;
+    case '*':
+    {
+        long long a = stack_pop(&st);
+        stack_push(&st, a * num);
+        break;
+    }
+    case '/':
+    {
+        long long a = stack_pop(&st);
+        // C 的整数除法向零截断
+        stack_push(&st, a / num);
+        break;
+    }
+    default:
+        break;
+    }
+
+    long long ans = 0;
+    // 栈中为已应用乘除的加减项，累加得到结果
+    while (!stack_empty(&st))
+        ans += stack_pop(&st);
+
+    printf("%lld\n", ans);
+
+    stack_free(&st);
+    free(s);
+    return 0;
+}