- use fgets, and remove the potential ‘\n’ in the string’s last postion.
- (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.