算术表达式的转换

http://acm.sdut.edu.cn/sdutoj/showproblem.php?pid=2484&cid=1182

写的代码很复杂

先转换成后缀式再建立表达式树

  1 #include <stdio.h>

  2 #include <stdlib.h>

  3 #include <ctype.h>

  4 

  5 #define MAXN 100

  6 int comp(char a, char b)

  7 {

  8     if(a == '(') return 0;

  9     if(a=='*' || a=='/') return 1;

 10     else if((a=='+' || a=='-') && (b == '+' || b == '-')) return 1;

 11     else return 0;

 12 

 13 }

 14 char st1[MAXN], st2[MAXN];

 15 

 16 typedef struct node

 17 {

 18     union

 19     {

 20         char operator1;

 21         char data;

 22     };

 23     struct node *l;

 24     struct node *r;

 25 } tree;

 26 typedef struct Tree_Stack

 27 {

 28     tree *buf[MAXN];

 29     int n;

 30 } treestack;

 31 treestack *create_empty_stack()

 32 {

 33     treestack *pstack;

 34 

 35     pstack = (treestack *)malloc(sizeof(treestack));

 36     pstack->n = -1;

 37 

 38     return pstack;

 39 }

 40 int push_stack(treestack *p, tree *data)

 41 {

 42     p->n++;

 43     p->buf[p->n] = data;

 44 

 45     return 0;

 46 }

 47 tree *pop_stack(treestack *p)

 48 {

 49     tree *data;

 50 

 51     data = p->buf[p->n];

 52     p->n --;

 53 

 54     return data;

 55 }

 56 int is_empty_stack(treestack *p)

 57 {

 58     if(p->n == -1)

 59         return 1;

 60     else

 61         return 0;

 62 }

 63 void srea1(char s[])

 64 {

 65     int i=0,top1=0,top2=0;

 66     while(s[i] != '#')

 67     {

 68         if(isalpha(s[i])) st1[top1++] = s[i];

 69         else if(top2 == 0) st2[top2++] = s[i];

 70         else if(s[i] == '(') st2[top2++] = s[i];

 71         else if(s[i] == ')')

 72         {

 73             while(st2[top2-1] != '(') st1[top1++] = st2[--top2];

 74             --top2;

 75         }

 76         else if(comp(st2[top2-1], s[i]))

 77         {

 78             st1[top1++] = st2[--top2];

 79             st2[top2++] = s[i];

 80         }

 81         else

 82         {

 83             st2[top2++] = s[i];

 84         }

 85         i++;

 86     }

 87     while(top2 != 0)

 88     {

 89         st1[top1++] = st2[--top2];

 90     }

 91 }

 92 tree *create_express_tree(char *str, treestack *p)

 93 {

 94     int i = 0;

 95     tree *current;

 96     tree *left, *right;

 97 

 98     while(str[i])

 99     {

100         if(str[i] >= 'a' && str[i] <= 'z')

101         {

102             current = (tree *)malloc(sizeof(tree));

103             current->data = str[i];

104             current->l = NULL;

105             current->r = NULL;

106             push_stack(p, current);

107         }

108         else

109         {

110             current = (tree *)malloc(sizeof(tree));

111             current->operator1 = str[i];

112             right = pop_stack(p);

113             left = pop_stack(p);

114             current->l = left;

115             current->r = right;

116             push_stack(p, current);

117         }

118         i++;

119     }

120     return p->buf[p->n];

121 }

122 void print_node(tree *p)

123 {

124     if(p->l== NULL && p->r == NULL)

125         printf("%c", p->data);

126     else

127         printf("%c", p->operator1);

128 }

129 

130 int visit_node(tree *p)

131 {

132     print_node(p);

133 

134     return 0;

135 }

136 

137 void PostOrder(tree *p)

138 {

139     if(p != NULL)

140     {

141         PostOrder(p->l);

142         PostOrder(p->r);

143         visit_node(p);

144     }

145 }

146 void InOrder(tree *p)

147 {

148     if(p != NULL)

149     {

150         InOrder(p->l);

151         visit_node(p);

152         InOrder(p->r);

153     }

154 }

155 

156 void PreOrder(tree *p)

157 {

158     if(p != NULL)

159     {

160         visit_node(p);

161         PreOrder(p->l);

162         PreOrder(p->r);

163     }

164 }

165 

166 int main()

167 {

168     tree *thead;

169     treestack *pstack;

170     int i = 0;

171     char buf[100];

172 

173     scanf("%s", buf);

174     srea1(buf);

175     pstack = create_empty_stack();

176     thead = create_express_tree(st1, pstack);

177 

178     PreOrder(thead);

179 

180     printf("\n");

181     InOrder(thead);

182     printf("\n");

183     PostOrder(thead);

184     printf("\n");

185     return 0;

186 }

View Code