[735] Asteroid Collision

一開始搞錯題目了！！！終於弄懂以後，又把方向（正向跟負向飛行）想的太難！

終於PASS以後又因為想要寫的漂亮 母歸玻

真是奸詐的題目 （吃不到葡萄說葡萄酸XD）

但光是前面想要把每種可能都考慮到的寫法，就會被面試刷掉了吧哈哈哈哈哈（奔入雨中）

/**

* Note: The returned array must be malloced, assume caller calls free().

*/

int* asteroidCollision(int* asteroids, int asteroidsSize, int* returnSize) {

int *stack = calloc (asteroidsSize, sizeof(int));

int head = -1;

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

{

if (head < 0 || ( (stack[head]<0 || stack[head]>0 && asteroids[i]> 0)))

{

stack[++head]=asteroids[i];

continue;

}

while (head>=0 && (stack[head] > 0))

{

if (abs(stack[head]) > abs(asteroids[i]))

break; //stack remain the same

if (abs(stack[head]) == abs(asteroids[i]))

{

head--; // remove both side

break;

}

if (abs(stack[head]) < abs(asteroids[i]))

{

head--;

if ((head < 0) || stack[head]<0)

{

stack[++head]= asteroids[i];

break;

}

}

}

}

*returnSize = head+1;

return stack;

}