java - 找不到符号-变量java

Question

我正在尝试在 Java 中执行以下程序我正在编写一个递归和迭代方法来计算 n 中所有奇数的总和至m

import java.util.Scanner;

public class AssignmentQ7 {

public static int recursivesum(int n, int m){

    if (n < m){
        int s = n;
        s += recursivesum(n+2, m);

    } else{
        if(m < n){
            int  s = m;
            s += recursivesum(m+2, n);

        }
    }
    return s;
}

public static int iterativesum(int n, int m){
    if(n < m){
        int s = n;
        for(int i = n; i <= m; i += 2){
            s += i; 
                    return s;
        }
    } else
        if(m < n){
            int s = m;
            for(int i = m; i <= n; i += 2){
            s += i; 
                    return s;
            }
        }

}

public static void main(String args[]){

    int n,m;

    Scanner in = new Scanner(System.in);

    System.out.println("Enter two numbers: ");
    n = in.nextInt();
    m = in.nextInt();

    while(n%2 == 0){
        System.out.println("Enter the first number again: ");
        n = in.nextInt();
    }

    while(m%2 == 0){
        System.out.println("Enter the second number again: ");
        m = in.nextInt();
    }

    System.out.println("The answer of the recursive sum is: " + recursivesum(n,m));
    System.out.println("The answer of the iterative sum is: " + iterativesum(n,m));
}
 }

我收到错误无法找到符号-变量 enter code here s。我不知道怎么了!有人可以帮忙吗？

Answer 1

这个方法有问题:

public static int recursivesum(int n, int m) {
    if (n < m) {
        int s = n; // Variable declared here... scoped to the if
        s += recursivesum(n+2, m);

    } else {
        if (m < n) {
            int  s = m; // Variable declared here... scoped to this if
            s += recursivesum(m+2, n);
        }
    }
    return s; // No such variable in scope!
}

您可以使用:

public static int recursivesum(int n, int m) {
    int s = 0; // See note below
    if (n < m) {
        s = n + recursivesum(n+2, m);

    } else {
        if (m < n) {
            s = m + recursivesum(m+2, n);
        }
    }
    return s;
}

我们必须给 s 一个明确的初始值，因为您当前没有任何代码处理 n 和 m 的情况是平等的。目前还不清楚你想做什么。

另一种选择是从 if 语句返回，就像在 iterativesum 中所做的那样...尽管您将再次需要考虑如果 m == n:

public static int recursivesum(int n, int m) {
    if (n < m) {
        // You don't even need an s variable!
        return n + recursivesum(n+2, m);   
    } else if (m < n) {
        // Simplified else { if { ... } } to else if { .... }
        return m + recursivesum(m+2, n);
    } else {
        // What do you want to return here?
    }
}

请注意，您在 iterativesum 中遇到了同样的问题 - 编译器此时应该向您提示并非所有路径都返回值。您期望 iterativesum(3, 3) 做什么？