Molecular weight (Molar mass,acm/icpc Seoul 2007,uva 1586)

Problem Solving Ideas:

1. Record the molecular weight with a double array

2. Store the string in a character array, scan from the back, always remember "letter", the next character to determine whether it is a number, if it is a number: With an integer record, this code with the sum, subscript + +.

Judge to see if the number is recorded, that is, whether the sum has entered the while loop and is assigned, if not assigned, the next character is not a number, and the W (total record) value is directly assigned to the current character's weight (molecular weight), which is the value in the double array. If the value is assigned, the description character is followed by a number, the sum holds the number, and the W is assigned, but at this time the weight (molecular weight) of the current character that is assigned sum.

3. Finally the entire string loop is complete, the output total record W can be.

#include <stdio.h>int main (void) {    double darr[200];    int n,sum,p;    Double W;    Char c,carr[1000];    darr[' C ']=12.01;    darr[' H ']=1.008;    darr[' O ']=16.00;    darr[' N ']=14.01;    scanf ("%d", &n);    while (n--)    {        p=0;        w=0;        scanf ("%s", Carr);        while (carr[p]!= ')        {            sum=0;            C=CARR[P];            p++;            while (carr[p]>= ' 0 ' && carr[p]<= ' 9 ')            {                sum=sum*10+carr[p]-' 0 ';                p++;            }            if (sum)                w=w+sum* (Darr[c]);            else                w+= (darr[c]);        }        printf ("%.3f\n", W);    }    return 0;}

　　

Molecular weight (Molar mass,acm/icpc Seoul 2007,uva 1586)