這個禮拜上課時提到了 Stack

找了一題 UVa 的題目

透過 C 使用 Linked List 實作 Stack

Uva 442 Matrix Chain Multiplication

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/*****************************************
Filename:p442.c
Author:Willy Chen(willychen.org)
Date:2018.04.19
*****************************************/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

struct m{
char name;
int row;
int col;
};
typedef struct m Matrix;

struct s{
Matrix matrix;
struct s* downPtr;
};
typedef struct s Stack;

// Check if the stack is empty
int isEmpty(Stack **stack){
if(stack == NULL)
return 1;
else
return 0;
}

void push(Stack **stack,Matrix matrix){
//printf("Insert:%c %d %d\n",name,row,col);
Stack * new_stack = (Stack*) malloc(sizeof(Stack));
if(new_stack!=NULL){
new_stack->matrix = matrix;
new_stack->downPtr = (*stack);
(*stack) = new_stack;
}
}

// Check if stack is empty before pop function
Matrix pop(Stack **stack){
Stack *top = *stack;
Matrix matrix = top->matrix;
*stack = (*stack)-> downPtr;
free(top);
return matrix;
};

// Show the stack
void show(Stack **stack){
Stack *now = *stack;
while(now!=NULL){
Matrix matrix = now->matrix;
printf("%c %d %d -> ",matrix.name,matrix.row,matrix.col);
now = now->downPtr;
}
printf("NULL\n");
}

int main(){
int num;
scanf("%d\n",&num);
//printf("num:%d\n",num);
Matrix matrix[30];

for(int i=0;i<num;i++){
char name;
int row,col;
scanf("%c%d%d\n",&name,&row,&col);
matrix[i].name = name;
matrix[i].row = row;
matrix[i].col = col;
}

// Show all matrices
/*
for(int i=0;i<num;i++){
printf("%c %d %d\n",matrix[i].name,matrix[i].row,matrix[i].col);
}
*/

char command[10000]={0};
while(scanf("%s",command)!=EOF){
int ans=0;
int flag=1;
//stack of matrix
Stack* stack = NULL;

int len = strlen(command);
for(int i=0;i<len;i++){
if(command[i]=='(')
continue;
else if(command[i]==')'){
// Pop 2 matrices and calculate
Matrix m1,m2;
if(isEmpty(&stack)){
flag=0;
break;
}else{
m2 = pop(&stack);
}
if(isEmpty(&stack)){
flag=0;
break;
}else{
m1 = pop(&stack);
}
if(m1.col!=m2.row){
flag=0;
break;
}
ans += m1.row*m1.col*m2.col;
m1.col = m2.col;
// Push the result on top of stack
push(&stack,m1);
}else{
// Find Matrix
int j=0;
for(j=0;j<num;j++)
if(command[i]==matrix[j].name)
break;
// Push Matrix on the top of stack
push(&stack,matrix[j]);
}
//show(&stack);
}
if(flag)
printf("%d\n",ans);
else
printf("error\n");

// Reset
memset(command,0,sizeof(command)/sizeof(char));
}

return 0;
}

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