Likou 1047. Delete all adjacent duplicates in the string-stack

1047. Remove all adjacent duplicates in a string

Given a string S consisting of lowercase letters, the duplicate deletion operation will select two adjacent and identical letters and delete them.

Repeat the deduplication operation on S until it can no longer be deleted.

Return the final string after completing all the deduplication operations. The answer is guaranteed to be unique.

示例：

输入："abbaca"
输出："ca"
解释：
例如，在 "abbaca" 中，我们可以删除 "bb" 由于两字母相邻且相同，这是此时唯一可以执行删除操作的重复项。之后我们得到字符串 "aaca"，其中又只有 "aa" 可以执行重复项删除操作，所以最后的字符串为 "ca"。

提示：

1 <= S.length <= 20000
S 仅由小写英文字母组成。

answer:

The typical first-in-last problem can be solved by directly building a stack on the original array.

Code:

char * removeDuplicates(char * S){
    
    
    int top = 0;
    for(int i=0;i<strlen(S);i++)
    {
    
    
        if(top==0)
        {
    
    
            S[top]=S[i];
            top++;
        }
        else
        {
    
    
            if(S[top-1]==S[i])
            {
    
    
                top--;
            }
            else
            {
    
    
                S[top]=S[i];
                top++;
            }
        }
    }
    S[top]='\0';
    return S;
}