Question

int arr[] = {21, 44, 56, 76, 89, 91, 102, 120, 143, 167, 242, 291}; //array.length == 11.
int goal = 143;
int i = (arr.length - 1)/2;
int upper = arr.length -1;
int lower = 0;
int found = 0;
boolean foundYes = false;
int j;
while (foundYes = false) {
    if(arr[i] > goal) {
        upper = i;
        i = (upper - lower)/2;
    } else if(arr[i] < goal) {
        lower = i;
        i = (upper - lower)/2;
    } else if(arr[i] == goal) {
        found = i;
        foundYes = true;
        break;
    }
}
System.out.println(found);

我正在尝试在数组中找到值为143的索引。所以arr [x] = 143，其中找到x是目标

我尝试了带有断点的调试器，但它并没有给我很多信息或细节。

我从调试器获得的内容：因此它检测到arr[i] == arr[5] == 91 < 143但它从未更改任何内容，并且找到的内容返回为found==0这里有什么问题？

编辑：我已经开始工作了：

   int arr[] = {21, 44, 56, 76, 89, 91, 102, 120, 143, 167, 242, 291}; //array.length == 11.
    int goal = 143;
    int i = (arr.length - 1)/2; //first arr[i] = 91.
    int upper = arr.length -1;
    int lower = 0;
    int found = 0;
    boolean foundYes = false;
    int j;
    while (foundYes == false) {
        if(arr[i] > goal){
            upper = i;
            i = upper + (upper - lower)/2;
        }
        else if(arr[i] < goal){
            lower = i;
            i = lower + (upper - lower)/2;
        }
        else if(arr[i] == goal){
             found = i;
            foundYes = true;
            break;
        }
    }
    System.out.println(found);
}

}

Answer 1

有两个问题。首先，while中的语法不正确，这就是您的程序没有被发送到无限循环的原因。您想要foundYes == false，而不是foundYes = false。第二个问题（您可能尚未遇到）是您如何设置i。假设upper等于8且lower等于7。 i变成了什么？看看那个，看看你是否可以从中找到它。

二进制搜索有序数组问题

1 个答案: