LeetCode刷题实战170：两数之和 III - 数据结构设计
Design and implement a TwoSum class. It should support the following operations: add
and find.
add(input) – Add the number input to an internal data structure.
find(value) – Find if there exists any pair of numbers which sum is equal to the value.
题意
示例 1:
add(1); add(3); add(5);
find(4) -> true
find(7) -> false
示例 2:
add(3); add(1); add(2);
find(3) -> true
find(6) -> false
解题
在类下面声明属性
在构造函数方法里初始化类的属性
在其他函数对属性和函数进行调用完成功能
class TwoSum {
//属性
private ArrayListnums;
private boolean is_sorted;
/** Initialize your data structure here. */
public TwoSum(){
this.nums = new ArrayList();
is_sorted =false;
}
/** Add the number to an internal data structure.. */
public void add(int number) {
this.nums.add(number);
this.is_sorted = false;
}
/** Find if there exists any pair of numbers which sum is equal to the value. */
public boolean find(int value) {
if (!this.is_sorted) {
//调用Collections类进行数组排序
Collections.sort(this.nums);
}
int low = 0, high = this.nums.size() - 1;
while (low < high) {
int twosum = this.nums.get(low) + this.nums.get(high);
if (twosum < value)
low += 1;
else if (twosum > value)
high -= 1;
else
return true;
}
//默认返回false
return false;
}
}