[Molar Mass, ACM/ICPC Seoul 2007, UVA1586]

主要是固定位 的思想，这是最后的代码，不过中间一直wrong answer，一直找不出，原来是15写成了14.

#include <stdio.h>
#include <string.h>int isnum(char c) {return c>='0' && c<='9';
}int main() {int T;char s[85];//freopen("test.txt", "r", stdin);double wei[15];wei['C'- 'A'] = 12.01;wei['H'- 'A'] = 1.008;wei['O'- 'A'] = 16.00;wei['N'- 'A'] = 14.01;scanf("%d", &T);while(T--) {scanf("%s", s);int len = strlen(s);double sum = 0;for(int i=0; s[i]!='\0'; ++i) {if(i+3 == len) {if(isnum(s[i+1]) && isnum(s[i+2])) {sum += wei[s[i] - 'A'] * ((s[i+1] - '0')*10 + (s[i+2] - '0'));break;}else if(isnum(s[i+1])) {sum += wei[s[i] - 'A'];i++;}}if(i+2 == len && isnum(s[i+1])) {sum += wei[s[i] - 'A'] * (s[i+1] - '0');break;}if(isnum(s[i+1]) && isnum(s[i+2])) {sum +=  wei[s[i] - 'A'] * ((s[i+1] - '0')*10 + (s[i+2] - '0'));i+=2;}else if(isnum(s[i+1])) {sum +=  wei[s[i] - 'A'] * (s[i+1] - '0');i++;}else {sum +=  wei[s[i] - 'A'];}}printf("%.3f\n", sum);}return 0;
}