A circus is designing a tower routine consisting of people standing atop one another’s shoulders. For practical and aesthetic reasons, each person must be both shorter and lighter than the person below him or her. Given the heights and weights of each person in the circus, write a method to compute the largest possible number of people in such a tower.

EXAMPLE:

Input (ht, wt): (65, 100) (70, 150) (56, 90) (75, 190) (60, 95) (68, 110)

Output: The longest tower is length 6 and includes from top to bottom: (56, 90) (60,95) (65,100) (68,110) (70,150) (75,190)

The problem looks like sorting, we can sort the person by height, if the height are the same, we sort by weight. Then we go through the sorted to find the longest continuous sequence.

public static int longestSeq(Person[] p) {
Arrays.sort(p, new Comparator<Person>() {
@Override
public int compare(Person p1, Person p2) {
if (p1.height > p2.height)
return 1;
else if (p1.height < p2.height)
return -1;
else {
if (p1.weight > p2.weight)
return 1;
else if (p2.weight < p2.weight)
return -1;
}
return 0;
}
});
int maxLen = 1;
int len = 1;
Person pre = p[0];
for (int i = 1; i < p.length; i++) {
Person cur = p[i];
if (onTop(pre, cur)) {
len++;
}
else {
len = 1;
}
maxLen = Math.max(maxLen, len);
}
return maxLen;
}
private static boolean onTop(Person p1, Person p2) {//return true if person1 can be on top of person2
return (p1.height <= p2.height && p1.weight <= p2.weight);
}

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