Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
For example, given n = 3, a solution set is:
[
"((()))",
"(()())",
"(())()",
"()(())",
"()()()"
]
方法
采用递归的方法
void addParenthesisRecursively(int left, int right, char* str,
char**result, int* returnSize, int n)
其中left表示可以追加多少左括号，right表示可以追加多少右括号，str表示当前括号组成的字符串。每往left里追加(后，left-1，right+1; 每往str里追加)后，right-1
c代码
#include <string.h>
#include <stdlib.h>
#define SIZE 10000
void addParenthesisRecursively(int left, int right, char* str, char**result, int* returnSize, int n) {
if((left == 0) && (right == 0))
result[(*returnSize)++] = str;
else {
char* newStr = (char *)malloc(sizeof(char) * (2*n+1));
if(left > 0) {
strcpy(newStr, str);
addParenthesisRecursively(left-1, right+1, strcat(newStr, "("), result, returnSize, n);
}
if(right > 0) {
strcpy(newStr, str);
addParenthesisRecursively(left, right-1, strcat(newStr, ")"), result, returnSize, n);
}
}
}
/**
* Return an array of size *returnSize.
* Note: The returned array must be malloced, assume caller calls free().
*/
char** generateParenthesis(int n, int* returnSize) {
char** result = (char **)malloc(sizeof(char *) * SIZE);
addParenthesisRecursively(n, 0, "", result, returnSize, n);
return result;
}
int main() {
int returnSize = 0;
char** result = generateParenthesis(3, &returnSize);
assert(strcmp("((()))", result[0]) == 0);
assert(returnSize == 5);
return 0;
}
