题解 | #没有重复项数字的全排列#

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param num int整型一维数组 
 * @param numLen int num数组长度
 * @return int整型二维数组
 * @return int* returnSize 返回数组行数
 * @return int** returnColumnSizes 返回数组列数
 */
void back(
        int* num,
        int numLen,
        int** res,
        int* path,
        int pathsize,
        int* used,
        int* len       
    ){
        if(pathsize == numLen){
            int *temp = (int *)malloc(sizeof(int) * numLen);
            memcpy(&temp[0], &path[0], sizeof(int) * numLen);
            res[len[0]] = temp;
            len[0]++;
            return;
        }
        for(int i = 0 ; i < numLen ; i++){
            if(used[i] == 1) continue;
            path[pathsize] = num[i];
            used[i] = 1;
            back(num,numLen,res,path,pathsize + 1,used,len);
            used[i] = 0;
        }
    }
int** permute(int* num, int numLen, int* returnSize, int** returnColumnSizes ) {
    // write code here
    if(numLen == 0) return NULL;
    int sum = 1;
    for(int i = 1 ; i <= numLen ; i++) sum *= i;
    *returnSize = sum;
    int* col = (int*)malloc(sizeof(int)*sum);
    for(int i = 0 ; i < sum ; i++) col[i] = numLen;
    *returnColumnSizes = col;
    int* path = (int*)malloc(sizeof(int)*numLen);
    int* used = (int*)malloc(sizeof(int)*numLen);
    int** res = (int**)malloc(sizeof(int*)*sum);
    int len = 0;
    for(int i = 0 ; i < numLen ; i++){
        used[i] = 0;
    }
     back(num,numLen,res,path,0,used,&len);
    return res;
}