巢狀 if() ... else VS if() .. else Ladder

與 if()...else 梯形圖相比，巢狀的 if()...else 語句需要更多的執行時間（它們更慢），因為巢狀的 if()...else 語句在滿足外部條件 if() 語句時檢查所有內部條件語句，而 if()..else 梯形圖將在任何一個時間點停止條件測試 if() 或 else if() 條件語句為真。

一個 if()...else 階梯：

#include <stdio.h>

int main(int argc, char *argv[])
{
  int a, b, c;
  printf("\nEnter Three numbers = ");
  scanf("%d%d%d", &a, &b, &c);
  if ((a < b) && (a < c))
  {
    printf("\na = %d is the smallest.", a);
  }
  else if ((b < a) && (b < c))
  {
    printf("\nb = %d is the smallest.", b);
  }
  else if ((c < a) && (c < b))
  {
    printf("\nc = %d is the smallest.", c);
  }
  else
  {
    printf("\nImprove your coding logic");
  }
  return 0;
}

在一般情況下，被認為比同等的巢狀 if()...else 更好：

#include <stdio.h>

int main(int argc, char *argv[])
{
  int a, b, c;
  printf("\nEnter Three numbers = ");
  scanf("%d%d%d", &a, &b, &c);
  if (a < b)
  {
    if (a < c)
      {
        printf("\na = %d is the smallest.", a);
      }
    else
      {
        printf("\nc = %d is the smallest.", c);
      }
  }
  else
  {
    if(b < c)
    {
      printf("\nb = %d is the smallest.", b);
    }
    else
    {
      printf("\nc = %d is the smallest.", c);
    }
  }
  return 0;  
}