[402] Remove K Digits

Corner case 很多ㄟ

寫一寫就覺得怒了Orz

先這樣好了QQ

char* removeKdigits(char* num, int k) {

int len = strlen (num);

char* ret = calloc(len+1, sizeof(char));

int top = -1;

for (int i=0; i<len ; i++)

{

while (top >=0 && num[i]< ret[top] && k>0)

{

top--;

k--;

}

ret[++top]=num[i];

}

while (k>0 && top >=0)

{

k--;

top--;

}

ret[top+1]='\0';

if (top < 0)

return "0";

top = 0;

while (ret[top]=='0')

top++;

if (top>=strlen(ret))

return "0";

return (ret+top);

}