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KStacks.java
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75 lines (64 loc) · 1.93 KB
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package learn.ds.stack;
import java.util.Arrays;
/**
* @author Varma Penmetsa
*
* https://www.byte-by-byte.com/nstacks/
*/
public class KStacks {
int[] topOfStack;
int[] stackArray;
int[] availIndex;
int nextAvail = 0;
KStacks(int k, int n){
topOfStack = new int[k];
stackArray = new int[n];
availIndex = new int[n];
Arrays.fill(stackArray, 0);
Arrays.fill(topOfStack, -1);
int len = availIndex.length;
for (int i = 0; i < len; i++) {
availIndex[i] = i+1;
}
availIndex[len-1] = -1;
}
public void push(int k, int val){
if(nextAvail==-1){
System.out.println("Stack is full");
return;
}
stackArray[nextAvail] = val;
int prevTopOfStack = topOfStack[k];
topOfStack[k] = nextAvail;
int prevAvailIndex = availIndex[nextAvail];
availIndex[nextAvail] = prevTopOfStack;
nextAvail = prevAvailIndex;
}
public Integer pop(int k){
if(topOfStack[k] == -1){
System.out.println("Nothing to pop");
return topOfStack[k];
}
int ret = stackArray[topOfStack[k]];
int prevTopStack = topOfStack[k];
int prevAvailIndex = availIndex[topOfStack[k]];
availIndex[topOfStack[k]]= nextAvail;
topOfStack[k] = prevAvailIndex;
nextAvail = prevTopStack;
return ret;
}
public static void main(String[] args) {
KStacks ks = new KStacks(3,6);
ks.push(0,5);
ks.push(0,9);
ks.push(1,5);
ks.push(1,7);
ks.pop(0);
ks.push(0,11);
ks.push(2,1);
System.out.println("topOfStack: "+Arrays.toString(ks.topOfStack));
System.out.println("stackArray: "+Arrays.toString(ks.stackArray));
System.out.println("AvailIndex: "+Arrays.toString(ks.availIndex));
System.out.println("nextAvail: "+ks.nextAvail);
}
}