UVA327- Evaluating Simple C Expressions

思路：主要在要開兩個數組，一個數組存數改變前的值，另一個數組存數改變後的值

#include<stdio.h>#include<string.h>#include<ctype.h>#include<stdlib.h>int main(){char str[200];while (gets(str) != NULL) {printf("Expression: ");puts(str);char s[200];memset(s, 0, sizeof(s));int num1[26], num2[26], vis[26];int cnt = 0;for(int i = 0;i < strlen(str); i++)if (str[i] == '+' || str[i] == '-' || isalpha(str[i]))s[cnt++] = str[i];for(int i = 0;i < 26; i++) {num1[i] = i + 1;num2[i] = i + 1;vis[i] = 0;}for(int i = 0;i < cnt; i++) {if (isalpha(s[i]))vis[s[i] - 'a'] = 1;if (s[i] == '+' && s[i + 1] == '+' && isalpha(s[i + 2])) {vis[s[i + 2] - 'a'] = 1;num1[s[i + 2] - 'a']++;num2[s[i + 2] - 'a']++;s[i] = '#';s[i + 1] = '#';}if (s[i] == '-' && s[i + 1] == '-' && isalpha(s[i + 2])) {vis[s[i + 2] - 'a'] = 1;num1[s[i + 2] - 'a']--;num2[s[i + 2] - 'a']--;s[i] = '#';s[i + 1] = '#';}if (isalpha(s[i]) && s[i + 1] == '+' && s[i + 2] == '+') {vis[s[i] - 'a'] = 1;num1[s[i] - 'a']++;s[i + 1] = '#';s[i + 2] = '#'; }if (isalpha(s[i]) && s[i + 1] == '-' && s[i + 2] == '-') {vis[s[i] - 'a'] = 1;num1[s[i] - 'a']--;s[i + 1] = '#';s[i + 2] = '#';}}int flag = 1, sum = 0;for(int i = 0;i < cnt ; i++) {if (isalpha(s[i]) && flag) {sum += num2[s[i] - 'a'];flag = 0;}else if (s[i] == '+' || s[i] == '-') {if (s[i] == '+') {for(int j = i; ; j++)if (isalpha(s[j])) {sum += num2[s[j] - 'a'];break;}}if (s[i] == '-') {for(int j = i; ; j++)if (isalpha(s[j])) {sum -= num2[s[j] - 'a'];break;}}}}printf("    value = %d\n", sum);for(int i = 0;i < 26; i++) {if (vis[i]) {printf("    %c = %d\n", i + 'a', num1[i]);}}}return 0;}