infix expression for suffix, then evaluated by suffix expression

Person: infix expression

Computer: suffix expression

The infix suffix is required and then calculated. Either step requires a stack:

For (3 + 4) x5-6

One infix turn suffix

The stack involved is used to store symbols such as "+-x/()"

Thought:

Meet the digital output; Meet the symbol into the stack

When the empty stack or symbol is the left parenthesis, it is directly into the stack;

When the operator is the symbol to be put into the stack is greater than the symbol in the stack is now in the stack than the operator is larger or the output of the stack, and then into the stack;

When the operator is a closing parenthesis, the symbol in the stack until the first opening parenthesis is stacked, and the unsigned symbol is output

Algorithm:

Infix expression is changed to postfix expression void Mid2after (char *a, char *&b) {int L=strlen (a); int i=0,j=0;sqstack S;initstack (s); while (i<l &&s.top>=-1) {if (a[i]>= ' 0 ' &&a[i]<= ' 9 ') {b[j++]=a[i++];if (a[i]< ' 0 ' | | A[i]> ' 9 ') b[j++]= ';} Else{if (s.top==-1| | a[i]== ' (') s.data[++s.top]=a[i++];else if (a[i]== ' * ' | | a[i]== '/') {while (s.data[s.top]== ' * ' | | s.data[s.top]== '/') {b[j++]=s.data[s.top--];} s.data[++s.top]=a[i++];} else if (a[i]== ' + ' | | a[i]== '-') {while (s.data[s.top]== ' + ' | | s.data[s.top]== '-' | | s.data[s.top]== ' * ' | | s.data[s.top]== '/') {b[j++]=s.data[s.top--];}      s.data[++s.top]=a[i++];} else if (a[i]== ') ') {I++;while (s.data[s.top]!= ' (') {b[j++]=s.data[s.top--];} s.top--;} else if (a[i]== ') i++;else {cout<< "Inlegal input!"; return;}}} while (s.top>-1) {b[j++]=s.data[s.top--];}}

Two-suffix evaluation

The suffix expression evaluation stack is primarily used to store numerical values

Thought:

Each meeting number is into the stack;

Meeting operator is the top two-bit operation of the stack, and the result is re-entered.

Note the suffix expression of the wood is enclosed in parentheses.

Algorithm:

suffix Evaluation int Get_after (char *b) {int L=strlen (b); Sqstack s;initstack (s); int I=0,ss;while (i<l&&s.top>=-1) { if (b[i]>= ' 0 ' &&b[i]<= ' 9 ') {     ss=0;while (b[i]>= ' 0 ' &&b[i]<= ' 9 ') {     int j=1;    j= (b[i]-' 0 ');    Ss=ss*10+j;     i++;    cout<<ss<< "";}   S.data[++s.top]=ss;} else {int t=s.data[s.top];    Switch (B[i])    {case ' + ': s.data[--s.top]=s.data[s.top]+t;break;     Case '-': s.data[--s.top]=s.data[s.top]-t;break;     Case ' * ': s.data[--s.top]=s.data[s.top]*t;break;     Case '/': {if (t==0) return-100;s.data[--s.top]=s.data[s.top]/t;break;              }     Case ": Break;    default:{cout<< "error! "<<B[I];RETURN-100;}    }    i++;}} if (s.top>-1) return s.data[s.top];}

infix expression for suffix, then evaluated by suffix expression