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psaitu/ArrayProducts.java

Created August 5, 2019 16:19
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ArrayProducts.java
import java.util.Arrays;
public class Main {
/**
*
* @param arr
*
*
* [1, 2, 3, 4]
*
* [1, 0, 0, 0]
*
* [0, 0, 0, 1]
*
*
* l: [1, 1, 2, 6]
*
* r: [24, 12, 4, 1]
*
*
* [1, 2, 3, 4]
*
* [a(0), a(1), a(2), a(3)]
*
*
* p: [a(1) * a(2) * a(3), a(0) * a(2) * a(3), a(0) * a(1), a(3), a(0) * a(1) * a(2)]
*
* l: [1, a(0), a(1) * a(0), a(2) * a(1) * a(0)]
*
* r: [a(1) * a(2) * a(3), a(2) * (a3), a(3), 1]
*
*
*/
public static void productArray(int arr[]) {
int n = arr.length;
int[] left = new int[n];
int[] right = new int[n];
int[] product = new int[n];
left[0] = 1;
right[n -1] = 1;
for(int i = 1; i < n; i++) {
left[i] = left[i -1] * arr[i - 1];
}
for(int j = n - 2; j >= 0; j--) {
right[j] = arr[j + 1] * right[j + 1];
}
for(int k = 0; k < n; k++) {
product[k] = left[k] * right[k];
}
for(int l = 0; l < n; l++) {
System.out.print(product[l] + ", ");
}
}
public static void prodArraySpace(int[] arr) {
int n = arr.length;
int temp = 1;
int[] product = new int[n];
for(int i = 0; i < n; i++) {
product[i] = 1;
}
// [1, 2, 3, 4]
for(int i = 0; i < n; i++) {
product[i] *= temp;
temp *= arr[i];
}
System.out.println(Arrays.toString(product));
temp = 1;
for(int j = n - 1; j >= 0; j--) {
product[j] *= temp;
temp *= arr[j];
}
System.out.println(Arrays.toString(product));
for(int l = 0; l < n; l++) {
System.out.print(product[l] + ", ");
}
}
public static void main(String[] args) {
int[] a = new int[]{1, 2, 3, 4};
prodArraySpace(a);
}
}
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