Best way to calculate the nearest point from another point? - ios

Question

I have four point say _pointA _pointB _pointC _pointD. I want to find the nearest point from the current point. I had something like this but it sometimes gives wrong reasult.
Problem : When i near to pointA it gives pointC
CGPoint neastPoint=CGPointZero;
for (int i=0; i<3; i++) {
CGFloat x;
CGFloat y;
CGFloat currntDistance;
if (i==0){
x=(pointA.x-currentPoint.x) *(pointA.x-currentPoint.x);
y=(pointA.y-currentPoint.y)*(pointA.y-currentPoint.y);
currntDistance =sqrtf(x+y);
distance=currntDistance;
neastPoint=pointA;
}
else if (i==1){
x=(pointB.x-currentPoint.x) *(pointB.x-currentPoint.x);
y=(pointB.y-currentPoint.y)*(pointB.y-currentPoint.y);
currntDistance =sqrtf(x+y);
if (distance>currntDistance) {
distance=currntDistance;
neastPoint=pointB;
}
}
else if (i==2){
x=(pointC.x-currentPoint.x) *(pointC.x-currentPoint.x);
y=(pointC.y-currentPoint.y)*(pointC.y-currentPoint.y);
currntDistance =sqrtf(x+y);
if (distance>currntDistance) {
distance=currntDistance;
neastPoint=pointC;
}
}
else {
x=(pointD.x-currentPoint.x) *(pointD.x-currentPoint.x);
y=(pointD.y-currentPoint.y)*(pointD.y-currentPoint.y);
currntDistance =sqrtf(x+y);
if (distance>currntDistance) {
distance=currntDistance;
neastPoint=pointD;
}
}
CurrentPoint : {44, 33.140846}
Point A : {71, 178}
Point B : {134, 178}
Point C : {133, 71}
Point D : {75, 67}
Nearast Point : {133, 71}

Answer 1

With the points that you have given, pointD is the closest to currentPoint.
It is not found by your code because
for (int i=0; i<3; i++) {
should be
for (int i=0; i<4; i++) {
to check all 4 points. As others have noticed, you can simplify your code,
for example
CGFloat distance = FLT_MAX; // start with some large value
CGPoint nearestPoint;
CGPoint points[] = { pointA, pointB, pointC, pointD };
for (int i = 0; i < 4; i++) {
CGFloat currentDistance = hypotf(points[i].x - currentPoint.x, points[i].y - currentPoint.y);
if (currentDistance < distance) {
distance = currentDistance;
nearestPoint = points[i];
}
}

Answer 2

Pseudo :
Point[] allPoints = {poinA,pontB,pointC,....,pointN}
int distance = Int.MAX_VALUE;
Point nearestPoint = null;
for(int i = 0 ; i < allPoints.count;i++){
if(pointA != allPoints[i]){
int currentDistance = getDistance(pointA,allPoints[i]);
if(currentDistance < distance){
distance = currentDistance;
nearestPoint = allPoints[i];
}
}
}
print("Nearest point is " + nearestPoint);