完成了表达式计算小程序

Chapter11/ds/line/compute/main.c

@@ -0,0 +1,149 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "sqstack.h"
+
+// !!! 课程不完整，程序未写完
+// TODO: snum和sop需要不同的datatype
+
+static void compute(sqstack *snum, int *op)
+{
+    datatype n1, n2, n;
+
+    st_pop(snum, &n2);
+    st_pop(snum, &n1);
+
+    switch (*op)
+    {
+    case '+': n = n1 + n2; break;
+    case '-': n = n1 - n2; break;
+    case '*': n = n1 * n2; break;
+    case '/': n = n1 / n2; break;
+
+    default: exit(1);
+    }
+    st_push(snum, &n);
+}
+
+static deal_bracket(sqstack *snum, sqstack *sop)
+{
+    datatype old_op;
+
+    st_top(sop, &old_op);
+
+    while (old_op != '(')
+    {
+        st_pop(sop, &old_op);
+        compute(snum, &old_op);
+        st_top(sop, &old_op);
+    }
+
+    st_pop(sop, &old_op);
+}
+
+static int get_pri(int op)
+{
+    switch (op)
+    {
+    case '(': return 0;
+    case '+':
+    case '-': return 1;
+    case '*':
+    case '/': return 2;
+    }
+}
+
+
+static void deal_op(sqstack *snum, sqstack *sop, char op)
+{
+    datatype old_op;
+
+    if (st_isempty(sop) || op == '(')
+    {
+        st_push(sop, &op);
+        return;
+    }
+
+    st_top(sop, &old_op);
+
+    if (get_pri(op) > get_pri(old_op))
+    {
+        st_push(sop, &op);
+        return;
+    }
+
+    while (get_pri(op) <= get_pri(old_op))
+    {
+        st_pop(sop, &old_op);
+        compute(snum, &old_op);
+        if (st_isempty(sop))
+            break;
+
+        st_top(sop, &old_op);
+    }
+    st_push(sop, &op);
+}
+
+
+int main()
+{
+    int      i;
+    char     str[] = "(11+3)*2-5";
+    sqstack *snum, *sop;
+    int      value = 0;
+    int      flag  = 0;
+    int      old_op;
+
+    snum = st_create();
+    if (NULL == snum)
+        exit(1);
+
+    sop = st_create();
+    if (NULL == sop)
+        exit(1);
+
+    while (str[i] != '\n')
+    {
+        if (str[i] >= '0' && str[i] <= '9')
+        {
+            value = 10 * value + (str[i] - '0');
+            flag  = 1;
+        }
+        else   // is a op
+        {
+            if (flag)
+            {
+                st_push(snum, &value);
+                flag  = 0;
+                value = 0;
+            }
+
+            if (str[i] == ')')
+            {
+                deal_bracket(snum, sop);
+            }
+            else   // ( + - * /
+            {
+                deal_op(snum, sop, str[i]);
+            }
+        }
+        i++;
+    }
+
+    if (flag)
+        st_push(snum, &value);
+
+    while (!st_isempty(sop))
+    {
+        st_pop(sop, &old_op);
+        compute(snum, &old_op);
+    }
+
+
+
+
+    st_destroy(snum);
+    st_destroy(sop);
+
+    exit(0);
+}