(algorithm) to determine whether two intervals overlap

Topic:

Determine if two intervals overlap

Ideas:

Assuming that the interval is expressed as [start,end], there are two intervals, a, B.

There are two types of relationships in two intervals: overlapping and non-overlapping

There are 4 overlapping cases, two types of intersection, two inclusions (it's easy to think, don't signal here)

There are two cases of non-overlap: A in front of B, a behind B

Therefore, it is easy to get the method of judging interval overlap:

1, positive judgment, list four kinds of overlapping cases, to meet one, then overlap;

2, reverse judgment, list two kinds of non-overlapping cases, if one is satisfied, then overlap;

The second method is obviously simpler.

Optimize forward judgment:

Consider the positive judgment of the four cases, in fact, as long as the Max (A.start,b.start) <=min (a.end,b,end), you can judge a B overlap. (Because the drawing is more troublesome, here does not indicate, can try on the paper)

Code:

#include <iostream>using namespace std;typedef struct{    int start;    int end;} Interval;bool isoverlap_1 (Interval interval1,interval interval2) {    if (Interval1.end<interval2.start | | Interval1.start>interval2.end)        return false;    return true;} BOOL Isoverlap_2 (Interval interval1,interval interval2) {    if (max (Interval1.start,interval2.start) <=min ( interval1.end,interval2.end))        return true;    return false;} int main () {    Interval interval1,interval2;    while (1) {        if (cin>>interval1.start && cin>>interval1.end && cin>> Interval2.start && cin>>interval2.end) {            if (isoverlap_2 (interval1,interval2))                cout< < "overlap" <<endl;            else                cout<< "Non-overlap" <<endl;        }    }    return 0;}

　　

(algorithm) to determine whether two intervals overlap