题目：

题解：

#define N 2000typedef struct {int data[30];;int top;
} Stack;void push(Stack *s, int e) { s->data[(s->top)++] = e; }int pop(Stack *s) { return s->data[--(s->top)]; }//多位数字串转换成int
int strToInt(char *s)
{char val[] = {'\0', '\0', '\0', '\0'};int result = 0;for(int i = 0; isdigit(s[i]); ++i)val[i] = s[i];for(int i = strlen(val) - 1, temp = 1; i >= 0; --i, temp *= 10)result += ((val[i] - '0') * temp);return result;
}char* decodeString(char *s)
{Stack magnification; magnification.top = 0;Stack position; position.top = 0;char *result = (char*)malloc(sizeof(char) * N);char *rear = result;for(int i = 0; s[i] != '\0'; ) {if(isdigit(s[i])) {push(&magnification, strToInt(&s[i]));while(isdigit(s[i]))++i;}else if(s[i] == '[') {push(&position, rear - result);++i;}else if(s[i] == ']') {char *p = result + pop(&position);int count = (rear - p) * (pop(&magnification) - 1);for(; count > 0; --count)*(rear++) = *(p++);++i;}else*(rear++) = s[i++];}*rear = '\0';return result;
}