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(" "); 181 InOrder(thead); 182 printf(" "); 183 PostOrder(thead); 184 printf(" "); 185 return 0; 186 }