baekjoon 4949 attempt1이 안되는 이유와 수정코드

<<<<attempt1>>>>

#include<stdio.h>
#include<string.h>
//():0 []:1 

int main(){
    int stack[105];
    int top = 0;
    char string[105];
    
    
    while(1){
        fgets(string,105,stdin);
        if(string[0]=='.'&&string[1]=='\n')
            return 0;
        for(int i=0;string[i]!='\0';i++){
            if(string[i]=='\n'){
                if(top==0)
                    printf("yes\n");
                else
                    printf("no\n");
                top=0;
            }
            else if(string[i]=='(')
                stack[top++] = 0;
            else if(string[i]=='[')
                stack[top++] = 1;
            else if(string[i]==')'){
                if(stack[top-1]==0)//////////*************top=0인 경우에 stack[-1]에 접근할 수 없으므로 틀림.
                    top--;
                else{
                    printf("no\n");
                    top = 0;
                    break;
                }
            }
            else if(string[i]==']'){
                if(stack[top-1]==1)//////////*************top=0인 경우에 stack[-1]에 접근할 수 없으므로 틀림.
                    top--;
                else{
                    printf("no\n");
                    top = 0;
                    break;
                }
            }
        }
    }
    return 0;
}

 

 

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반례를 찾으려고 하기 보다는 내 코드에 어떠한 문제가 발생할 수 있는지 기본적인것부터 확인해보자.

***배열의 경우에는 범위를 벗어나는 경우가 빈번히 발생하므로 이를 주의하도록 하자!!!

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<<<<수정코드>>>>

 

#include<stdio.h>
#include<string.h>
//():0 []:1 

int main(){
    int stack[105] = {-1,};
    int top = 0;
    char string[105];
    
    
    
    while(1){
        fgets(string,105,stdin);
        if(string[0]=='.'&&string[1]=='\n')
            return 0;
        for(int i=0;string[i]!='\0';i++){
            if(string[i]=='\n'){
                if(top==0)
                    printf("yes\n");
                else
                    printf("no\n");
                top=0;
                break;
            }
            else if(string[i]=='(')
                stack[top++] = 0;
            else if(string[i]=='[')
                stack[top++] = 1;
            else if(string[i]==')'){
                if(top>0){
                    if(stack[top-1]==0)
                        top--;
                    else{
                        printf("no\n");
                        top = 0;
                        break;
                    }
                }
                else{
                    printf("no\n");
                    top = 0;
                    break;
                }
            }
            else if(string[i]==']'){
                if(top>0){
                    if(stack[top-1]==1)
                        top--;
                    else{
                        printf("no\n");
                        top = 0;
                        break;
                    }
                }
                else{
                    printf("no\n");
                    top = 0;
                    break;
                }
            }
        }
    }
    return 0;
}