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49 lines (45 loc) · 1.41 KB
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Copy pathBinarySearch.java
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49 lines (45 loc) · 1.41 KB
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/**
* 二分查找,
* 查找在有序数组中某给定值的位置,
* 算法复杂度为O(logn);
*/
@SuppressWarnings("unused")
public class BinarySearch implements AlgorithmInGraph {
public void showAlgorithm() {
int [] array = new int[100];
for(int i=0;i<100;i++ ){
array[i] = i;
}
printSearchResult(array,45);
printSearchResult(array,105);
printSearchResult(array,0);
printSearchResult(array,99);
}
/**
* @param sortedArray 已经排序好的数组
* @param value 需要查询的值value
* @return 返回值在有序数组中的索引,如果数组中不存在这个值,则返回-1;
*/
private int doBinarySearch(int [] sortedArray,int value){
int right = sortedArray.length - 1;
int left = 0;
int middle;
//这里=号容易被忽略
while(right>= left){
middle = (left+right)/2;
if(sortedArray[middle] == value){
return middle;
}
else if(sortedArray[middle] < value){
left = middle+1;
}
else{
right = middle-1;
}
}
return -1;
}
private void printSearchResult(int [] array,int value){
System.out.println("在0-99的有序数组中," + value+"的位置是: \t" + doBinarySearch(array,value));
}
}