1. use fgets, and remove the potential ‘\n’ in the string’s last postion.
2. (main point) remove redundancy
   
   there must be a stack, at first sight, you need a stack of type myNode, but think deeper, matrix multiplication is valid only if A.c=B.r, then the num of elementary multiplication is A.r*A.c*B.c, note that since A.c=B.r for every contiguous pair of matrices, so we can store the first matrix’s r and c, and for the rest, we first check validation, if error, break, else just store B.c, the B.r is not to been stored, thus remove redundancy.
   
   //

#include <cstdio>

#include <cstring>

#include <algorithm>

#define MAXSIZE 1000

struct myNode{ int r,c; };

int main() {

#ifndef ONLINE_JUDGE

    freopen("in.txt","r",stdin);

#endif

    int n,i,ch,len,iserror,res, stk[MAXSIZE];

    char buf[MAXSIZE], *p;

    myNode matrices[26], *mat=matrices-'A';

    scanf("%d\n",&n);

    if(n<=0) return -1;

    for(i=0;i<n;++i) {

        ch=getchar();

        scanf("%d%d\n",&mat[ch].r,&mat[ch].c);

    }

    while(fgets(buf,MAXSIZE,stdin)) {

        len=strlen(buf);

        if(buf[len-1]='\n') buf[--len]=0;

        for(res=0,iserror=0, p=buf+1;*p!=0 && *p=='(';++p) {}

        if(*p!=0) {

            stk[0]=mat[*p].r, stk[1]=mat[*p].c;

            for(len=1, ++p;*p!=0;++p) {

                if(*p=='(') continue;

                else if(*p==')') {

                    --len;

                    res+=stk[len-1]*stk[len]*stk[len+1];

                    stk[len]=stk[len+1];

                }

                else {

                    if(mat[*p].r!=stk[len]) { iserror=1; break; }

                    stk[++len]=mat[*p].c;

                }

            }

            while(len>1) {

                --len;

                res+=stk[len-1]*stk[len]*stk[len+1];

                stk[len]=stk[len+1];

            }

        }

        if(iserror) puts("error");

        else printf("%d\n",res);

    }

    return 0;

}

版权声明：本文为博主原创文章，未经博主允许不得转载。// p.s. If in any way improment can be achieved, better performance or whatever, it will be well-appreciated to let me know, thanks in advance.