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ContinuesSequenceWithSum.java
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/
ContinuesSequenceWithSum.java
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import java.util.ArrayList;
/**
* Created by Yang on 2017/4/22.
* 题目描述
* 小明很喜欢数学,有一天他在做数学作业时,要求计算出9~16的和,他马上就写出了正确答案是100。
* 但是他并不满足于此,他在想究竟有多少种连续的正数序列的和为100(至少包括两个数)。没多久,
* 他就得到另一组连续正数和为100的序列:18,19,20,21,22。现在把问题交给你,你能不能也很快的
* 找出所有和为S的连续正数序列? Good Luck!
* 输出描述:
* 输出所有和为S的连续正数序列。序列内按照从小至大的顺序,序列间按照开始数字从小到大的顺序
*/
public class ContinuesSequenceWithSum {
public ArrayList<ArrayList<Integer>> findContinuousSequence(int sum) {
ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
if(sum < 3) {
return res;
}
int small = 1;
int big = 2;
int middle = (1+sum)/2;
int currSum = small + big;
while(small < middle) {
if(currSum == sum) {
res.add(printContinuousSequence(small, big));
}
while(currSum > sum && small < middle) {
currSum -= small;
small++;
if(currSum == sum) {
res.add(printContinuousSequence(small, big));
}
}
big++;
currSum += big;
}
return res;
}
private ArrayList<Integer> printContinuousSequence(int small, int big) {
ArrayList<Integer> sequence = new ArrayList<>();
for (int i = small; i <= big; i++) {
sequence.add(i);
}
return sequence;
}
public static void main(String[] args) {
ContinuesSequenceWithSum continuesSequenceWithSum = new ContinuesSequenceWithSum();
System.out.println(continuesSequenceWithSum.findContinuousSequence(9));
System.out.println(continuesSequenceWithSum.findContinuousSequence(100));
System.out.println(continuesSequenceWithSum.findContinuousSequence(0));
System.out.println(continuesSequenceWithSum.findContinuousSequence(4));
}
}