递归函数中的加法答案

【问题标题】：Addition in Recursion Function递归函数中的加法
【发布时间】：2016-03-07 07:43:35
【问题描述】：

我的代码是当数组中的数字为 1 时 +1 得分，当数组中的数字为 -1 时得分 -1。但是当我运行程序时它只返回0。递归本身没有无限循环，我不知道我在这里做错了什么。

#include <iostream>

using namespace std;

/* When the tile is -1, score--. When the tile is 1, score++. You cannot go outside the array nor can you go backwards */

/* + 2 through the array */
int jumping( int track[], int size, int location ){
static int score = 0;

if ( track[ location ] == 1 ){
    score++;
}
else if ( track[ location ] == -1 ){
    score--;
}

if (( location == size - 1 ) || ( track[ location + 1 ] == 0 )){
    return score;
}
else{
    jumping( track, size, location + 2 );
}
}

/* Run through the array by 1 */
int stepping( int track[], int size, int location ){
static int score = 0;

if ( track[ location ] == 1 ){
    score++;
}
else if ( track[ location ] == -1 ){
    score--;
}

if ( location == size - 1 ){
    return score;
}
else{
    stepping( track, size, location++ );
}
}

/* Is to calculate the maxium possible score for any given track, with any arrangement using recursion. */
int maxScore( int track[], int size, int location ){
int score = 0; //Keep track of score
int step = stepping( track, size, location );//score by stepping
int jump = jumping( track, size, location );//score by jumping

/* If step is higher or jump and replace according to the highest */
if ( step > jump ){
    score = step;
    return score;
}
else if ( jump > step ){
    score = jump;
    return score;
}
else if ( jump == step ){
    return score;
}
}

int main(){

int simple[2] = { 0, 0 };
int easy[8] = { 0, -1, 1, 1, -1, 1, -1, 0 };
int medium[25] = { 0, 1, 1, -1, -1, 1, 1, 1, -1, 1, -1, 0 };
int mediumhard[3] = { 0, 1, 0 };
int impossible[20] = { 0, -1, 1, -1, 1, 1, -1, 1, -1, 1, 1, -1, -1, -1,     1, 1, 1, -1, -1, 0 };
int insane[40] = { 0, -1, 1, -1, 1, 1, -1, 1, -1, 1, 1, -1, -1, -1, 1, 1, 1, -1, -1, -1,
                  1, -1, 1, -1, 1, 1, -1, 1, -1, 1, 1, -1, -1, -1, 1, 1, 1, -1, -1, 0 };

cout << "1. SIMPLE............................................... " << maxScore( simple, 2, 0 ) << endl;
cout << "2. EASY................................................. " << maxScore( easy, 8, 0 ) << endl;
cout << "3. MEDIUM............................................... " << maxScore( medium, 25, 0 ) << endl;
cout << "4. MEDIUM HARD.......................................... " << maxScore( mediumhard, 3, 0 ) << endl;
cout << "5. IMPOSSIBLE........................................... " << maxScore( impossible, 20, 0 ) << endl;
cout << "6. INSANE............................................... " << maxScore( insane, 40, 0 ) << endl;

return 0;
}

【问题讨论】：

您在条件 (if (( location = size - 1 )...) 中有一个分配。这是故意的吗？
另外，你可能想要return stepping(track,size,location++)，否则不会有明确的返回值
注意：赋值是在第二个 if 语句中以及在 stepping() 中。 if ( location = size - 1 ){
@Christian 这应该是在函数到达数组末尾时停止函数，而不是使用 if ( location
@RNar 好的，我会添加它并查看它的工作原理。

标签： c++ arrays loops if-statement recursion

【解决方案1】：

我发现了 3 个问题：

在跳跃中，你的退出条件应该是location >= size -2而不是location == size-1，因为你的跳跃步数是2
在跳跃和步进中，您应该在递归调用中添加一个返回值，例如 return jumping(track, size, location + 2);
在步进递归调用中，应该是stepping( track, size, ++location );而不是stepping( track, size, location++ );

Ideone：http://ideone.com/M0C68r

【讨论】：

【解决方案2】：

/* + 2 through the array */
int jumping( int track[], int size, int location ){
static int score = 0;

if ( track[ location ] == 1 ){
    score++;
}
else if ( track[ location ] == -1 ){
    score--;
}

/*** Need to assign recursion to score; also else condition has no return; suggest replacing with the following ***
if (( location == size - 1 ) || ( track[ location + 1 ] == 0 )){
    return score;
}
else{
    jumping( track, size, location + 2 );
}*/
/*** Also, you need to use size - 2 to prevent overrun ***/
if (( location < size - 2 ) && ( track[ location + 1 ] != 0 ))
    score += jumping( track, size, location + 2 );
return score;
}

/* Run through the array by 1 */
int stepping( int track[], int size, int location ){
static int score = 0;

if ( track[ location ] == 1 ){
    score++;
}
else if ( track[ location ] == -1 ){
    score--;
}

/*** Need to assign recursion to score; also else condition has no return; suggest replacing with the following ***
if ( location == size - 1 ){
    return score;
}
else{
    stepping( track, size, location++ );
}*/
if (location < size - 1)
    score += stepping( track, size, location++ );
return score;
}

/* Is to calculate the maxium possible score for any given track, with any arrangement using recursion. */
int maxScore( int track[], int size, , int location ){
int score = 0; //Keep track of score
int step = stepping( track, size, location );//score by stepping
int jump = jumping( track, size, location );//score by jumping

/* If step is higher or jump and replace according to the highest */
if ( step > jump ){
    score = step;
    //*** See Later *** return score;
}
else if ( jump > step ){
    score = jump;
    //*** See Later *** return score;
}
else /*** Don't need the if, as it is the only remaining condition *** if ( jump == step ) */{
    //*** Score is not set here, is this intentional ***
    //*** See Later *** return score;
}
return score;
}

【讨论】：