以下哪两个代码段更快？假设编译器没有进行优化。
null
C++
/* FIRST */ for (i = 0; i < 10; i++) for (j = 0; j < 100; j++) //do something // This code is contributed by Shubham Singh |
C
/* FIRST */ for (i=0;i<10;i++) for (j=0;j<100;j++) //do something |
蟒蛇3
# FIRST for i in range ( 10 ): for j in range ( 100 ): #do something # This code is contributed by shivani |
C++
/* SECOND */ for (i=0;i<100;i++) for (j=0;j<10;j++) //do something //This code is contributed by Shubham Singh |
C
/* SECOND */ for (i=0;i<100;i++) for (j=0;j<10;j++) //do something |
蟒蛇3
# SECOND for i in range ( 100 ): for j in range ( 10 ): # Do something # This code is contributed by shivani |
两个代码段都提供相同的功能，两个for循环中的代码在两个代码段中执行的次数相同。 如果我们仔细观察，就会发现第二个比第一个做更多的操作。它执行for循环的所有三个部分（赋值、比较和增量）的次数比第一个循环的相应部分多：
- 第二个执行赋值操作（j=0或i=0）101次，而第一个只执行11次。
- 第二个进行101+1100比较（i<100或j<10），而第一个进行11+1010比较（i<10或j<100）。
- 第二个执行1100个增量操作（i++或j++），而第一个执行1010个增量操作。
下面的代码统计第一次和第二次执行的增量操作的数量，并打印计数。
C++
// C++ program to count number of increment // operations in FIRST and SECOND #include<iostream> using namespace std; int main() { int c1 = 0, c2 = 0; /* FIRST */ for ( int i=0;i<10;i++,c1++) for ( int j=0;j<100;j++, c1++); /* SECOND */ for ( int i=0; i<100; i++, c2++) for ( int j=0; j<10; j++, c2++); cout << " Count in FIRST = " <<c1 << endl; cout << " Count in SECOND = " <<c2 << endl; getchar (); return 0; } |
JAVA
// Java program to count number of increment // operations in FIRST and SECOND import java.io.*; class GFG { public static void main (String[] args) { int c1 = 0 , c2 = 0 ; for ( int i= 0 ; i< 10 ;i++, c1++){ for ( int j= 0 ;j< 100 ;j++, c1++){} } for ( int i= 0 ;i< 100 ;i++, c2++){ for ( int j= 0 ;j< 10 ;j++, c2++){} } System.out.println( "Count in First = " +c1); System.out.println( "Count in SECOND = " +c2); } } |
蟒蛇3
# Python program to count number of increment # operations in FIRST and SECOND c1 = 0 c2 = 0 # FIRST for i in range ( 10 ): for j in range ( 100 ): c1 + = 1 c1 + = 1 # SECOND for i in range ( 100 ): for j in range ( 10 ): c2 + = 1 c2 + = 1 print ( "Count in FIRST = " ,c1) print ( "Count in SECOND = " ,c2) # This code is contributed by shivanisinghss2110 |
C#
// C# program to count number of increment // operations in FIRST and SECOND using System; class GFG{ public static void Main (String[] args) { int c1 = 0, c2 = 0; for ( int i = 0; i < 10; i++, c1++) { for ( int j = 0; j < 100;j++, c1++){} } for ( int i = 0; i < 100; i++, c2++) { for ( int j = 0; j < 10; j++, c2++){} } Console.WriteLine( "Count in First = " + c1); Console.WriteLine( "Count in SECOND = " + c2); } } // This code is contributed by shivanisinghss2110 |
Javascript
<script> // JavaScript program to count number of increment // operations in FIRST and SECOND let c1 = 0, c2 = 0; for (let i=0; i<10;i++, c1++){ for (let j=0;j<100;j++, c1++){} } for (let i=0;i<100;i++, c2++){ for (let j=0;j<10;j++, c2++){} } document.write( "Count in First = " +c1 + "<br>" ); document.write( "Count in SECOND = " +c2); // this code is contributed by shivanisinghss2110 </script> |
输出
Count in FIRST = 1010 Count in SECOND = 1100
下面的代码统计第一个和第二个执行的比较操作的数量
C++
//program to count the number of comparison //operations executed by FIRST and SECOND */ #include<iostream> using namespace std; int main() { int c1 = 0, c2 = 0; /* FIRST */ for ( int i=0; ++c1&&i<10; i++) for ( int j=0; ++c1&&j<100;j++); /* SECOND */ for ( int i=0; ++c2&&i<100; i++) for ( int j=0; ++c2&&j<10; j++); cout << " Count for FIRST " <<c1 << endl; cout << " Count for SECOND " <<c2 << endl; getchar (); return 0; } |
JAVA
/*package whatever //do not write package name here */ import java.io.*; class GFG { public static void main (String[] args) { int c1 = 0 , c2 = 0 ; for ( int i= 0 ; i<++c1 && i< 10 ;i++) { for ( int j= 0 ;j<++c1 &&j< 100 ;j++) { } } for ( int i= 0 ;i<++c2 && i< 100 ;i++) { for ( int j= 0 ;j<++c2 &&j< 10 ;j++) { } } System.out.println( "Count in FIRST = " +c1); System.out.println( "Count in SECOND = " +c2); } } |
蟒蛇3
#program to count the number of comparison #operations executed by FIRST and SECOND */ # FIRST c1 = 1 c2 = 1 i = 0 while (i < c1 and i < 10 ): j = - 1 c1 + = 1 while (j < c1 and j < 100 ): c1 + = 1 j + = 1 i + = 1 # SECOND i = 0 while (i < c2 and i < 100 ): j = - 1 c2 + = 1 while (j < c2 and j < 10 ): c2 + = 1 j + = 1 i + = 1 print ( " Count fot FIRST " , c1) print ( " Count fot SECOND " , c2) # This code is contributed by shivanisinghss2110 |
C#
/*package whatever //do not write package name here */ using System; class GFG { public static void Main (String[] args) { int c1 = 0, c2 = 0; for ( int i = 0; i < ++c1 && i < 10; i++) { for ( int j = 0; j < ++c1 && j < 100; j++) { } } for ( int i = 0; i < ++c2 && i < 100; i++) { for ( int j = 0; j < ++c2 && j < 10; j++) { } } Console.WriteLine( "Count in FIRST = " +c1); Console.WriteLine( "Count in SECOND = " +c2); } } // This code is contributed by shivanisinghss2110 |
Javascript
<script> /*package whatever //do not write package name here */ //program to count the number of comparison //operations executed by FIRST and SECOND */ let c1 = 0, c2 = 0; for (let i=0; i<++c1 && i<10;i++) { for (let j=0;j<++c1 &&j<100;j++) { } } for (let i=0;i<++c2 && i<100;i++) { for (let j=0;j<++c2 &&j<10;j++) { } } document.write( "Count in FIRST = " +c1 + "<br>" ); document.write( "Count in SECOND = " +c2); // this code is contributed by shivanisinghss2110 </script> |
输出
Count for FIRST 1021 Count for SECOND 1201
幸亏 Dheeraj 感谢你提出解决方案。 如果您发现任何答案/代码不正确，或者您想分享有关上述主题的更多信息，请写下评论。
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