打印在C程序中生成形如2^X - 1的数字的步骤

给定一个数字 n，我们必须使用异或运算来打印将数字制成 2^X-1 形式的步骤。

• 我们应该进行异或任意 2^M-1 的数字，其中 M 由您选择，在奇数步长。
• 在偶数步长，将数字增加 1

继续执行该步骤，直到n变为2^X-1，并打印所有步骤

示例

Input: 22
Output:
   Step 1 : Xor with 15
   Step 2: Increase by 1
   Step 3 : Xor with 7
   Step 4: Increase by 1
   Step 5 : Xor with 1
Input:7
Output: No Steps to be performed

算法

int find_leftmost_unsetbit(int n)
START
STEP 1 : DECLARE AND ASSIGN ind = -1, i = 1
STEP 2 : LOOP WHILE n
   IF !(n & 1) THEN,
      ASSIGN ind WITH i
   END IF
   INCREMENT i BY 1
   LEFT SHIFT n BY 1
END WHILe
STEP 3 : RETURN ind
STOP
void perform_steps(int n)
START
STEP 1 : DECLARE AND ASSIGN left = find_leftmost_unsetbit(n)
STEP 2 : IF left == -1 THEN,
   PRINT "No Steps to be performed"
   RETURN
END IF
STEP 3 : DECLARE AND ASSIGN step = 1
STEP 4 : LOOP WHILE find_leftmost_unsetbit(n) != -1
   IF step % 2 == 0 THEN,
      INCREMENT n BY 1
      PRINT "Step n : Increase by 1
"
   ELSE
      DECLARE AND ASSIGN m =
      find_leftmost_unsetbit(n)
      AND SET num = (pow(2, m) - 1)
      SET n = n ^ num
      PRINT "Step N : Xor with Num
   END IF
   INCREMENT step BY 1
END LOOP
STOP

示例

#include <stdio.h>
#include <math.h>
//To find the leftmost bit
int find_leftmost_unsetbit(int n){
   int ind = -1;
   int i = 1;
   while (n) {
      if (!(n & 1))
         ind = i;
      i++;
      n >>= 1;
   }
   return ind;
}
void perform_steps(int n){
   // Find the leftmost unset bit
   int left = find_leftmost_unsetbit(n);
   //If there is no bit
   if (left == -1) {
      printf("No Steps to be performed
");
      return;
   }
   // To count the number of steps
   int step = 1;
   // Iterate till number is in form of 2^x - 1
   while (find_leftmost_unsetbit(n) != -1) {
      // if the step is even then increase by 1
      if (step % 2 == 0) {
         n += 1;
         printf("Step %d: Increase by 1
", step);
      }
      // if the step is odd then xor with 2^m-1
      else {
         // Finding the leftmost unset bit
         int m = find_leftmost_unsetbit(n);
         int num = (int)(pow(2, m) - 1);
         n = n ^ num;
         printf("Step %d : Xor with %d
", step, num);
      }
      // To increase the steps
      step += 1;
   }
}
int main(){
   int n = 22;
   perform_steps(n);
   return 0;
}

输出

如果我们运行上面的程序，那么它将生成以下输出 -

Step 1 : Xor with 15
Step 2 : Increase by 1
Step 3 : Xor with 7
Step 4 : Increase by 1
Step 5 : Xor with 1

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