思路就是用栈模拟，不用开实体的栈，直接记一个top指针就行。
说说这题的细节：
1.tag标签里的内容不要动，原样输出。比如<p aa bb cc>，就这样输出就行，不要删空格。题目中说了you shouldn’t change anything of any tag.
2.标签之外的文本，文本内的空白符（空格，tab，回车），相邻单词之间用一个空格分隔开。文本与标签相邻的地方，不要有多余的空白符，就是说，文本与标签相邻的地方，除了一个回车以及缩进用的空白符之外，不要有任何空白符。
3.上一个case的</html>跟下一个case的<html>有可能在同一行，并且第一个<html>之前有可能有空白符
4.每行结尾不要有多余的空格
5.不要有空行
以下给出几组数据，空格用<SPACE>表示,tab键用<TAB>表示：
Input:
5 <TAB><html> <body> <h1>ACM ICPC</h1> <p>Hello<br/>World</p> </body></html> <html> <body><p><TAB> Asia Chengdu Regional </p><TAB> <p class="icpc"> ACM-ICPC</p></body></html> <html> <TAB> <TAB> </html><TAB><html> <p> <TAB> aa bb cc dafdadgsdfsa<TAB> afd </p> <TAB> </html><TAB><TAB> <html><body aslfja fdsafs<TAB>fdsafsa ><bb/></body></html>
Output
Case #1: <html> <body> <h1> ACM ICPC </h1> <p> Hello <br/> World </p> </body> </html> Case #2: <html> <body> <p> Asia Chengdu Regional </p> <p class="icpc"> ACM-ICPC </p> </body> </html> Case #3: <html> </html> Case #4: <html> <p> aa bb cc dafdadgsdfsa afd </p> </html> Case #5: <html> <body aslfja fdsafs fdsafsa > <bb/> </body> </html>
代码
#include <cstdio> #include <cstring> #include <cstdlib> #define IN 0 #define OUT 1 #define START 0 #define END 1 using namespace std; const int MAXN = 210000; char str[MAXN]; char tmp[MAXN]; char tag[MAXN]; bool CheckEnd( char *s, int len ) { if ( s[len-6] == '<' && s[len-5] == '/' && s[len-4] == 'h' && s[len-3] == 't' && s[len-2] == 'm' && s[len-1] == 'l' && s[len] == '>' ) return true; return false; } int chuli( char *s, int len ) { int i = 0, j = 0; while ( i < len && (s[i] == ' ' || s[i] == 9 || s[i] == ' ') ) ++i; while ( i < len ) { s[j] = s[i]; if ( s[i] == '>' ) { ++i; while ( s[i] == ' ' || s[i] == 9 || s[i] == ' ' ) ++i; } else ++i; ++j; } s[j] = ' '; return j; } int DeleteSpace( char *s, int len ) { int i = 0, j = 0; while ( i < len ) { if ( s[i] == '<' ) { if ( j - 1 >= 0 && ( s[j - 1] == ' ' || s[j - 1] == 9 ) ) s[j - 1] = s[i++]; while ( i < len && s[i] != '>' ) { s[j++] = s[i++]; } s[j++] = s[i++]; } else if ( s[i] == ' ' || s[i] == 9 ) { s[j++] = ' '; while ( i < len && ( s[i] == ' ' || s[i] == 9 ) ) ++i; } else s[j++] = s[i++]; } s[j] = ' '; return j; } void solved( char* s, int len ) { //puts(s); int top = 0; int i = 0; while ( i < len ) { if ( s[i] == '<' ) { int j = 0; while ( s[i] != '>' ) { tag[j++] = s[i++]; } tag[j++] = s[i++]; tag[j] = ' '; if ( tag[1] == '/' ) { --top; for ( int k = 0; k < top; ++k ) putchar(' '); } else { for ( int k = 0; k < top; ++k ) putchar(' '); ++top; } if ( tag[j-2] == '/' ) --top; puts(tag); } else { for ( int k = 0; k < top; ++k ) putchar(' '); while ( i < len && s[i] != '<' ) { putchar(s[i]); ++i; } puts(""); } } return; } int main() { int T, cas = 0; //freopen( "in.txt", "r", stdin ); //freopen( "s.txt", "w", stdout ); scanf( "%d", &T ); printf( "Case #%d: ", ++cas ); int len = 0; while ( gets(tmp) != NULL ) { strcpy( &str[len], tmp ); len += strlen(tmp); str[len++] = ' '; } str[len - 1] = ' '; //puts(str); int j = 0; for ( int i = 0; i < len; ) { tmp[j++] = str[i++]; if ( j > 6 && CheckEnd( tmp, j - 1 ) ) { tmp[j] = ' '; --T; //printf( "T = %d ", T ); solved( tmp, DeleteSpace( tmp, chuli( tmp, j ) ) ); j = 0; if ( T ) printf( "Case #%d: ", ++cas ); } } return 0; }