Class weightedOutput{ Random rand; public int probOutput(int[] array){ // prefix int[] prefix = new int[array.length + 1]; prefix[0] = 0; for(int i = 1; i < array.length; i++){ prefix[i] = prefix[i - 1] + array[i - 1]; } int rand = rand.nextInt(prefix[prefix.length - 1]); int res = binarySearch (prefix, rand); // index of 9 return array[res - 1]; } } private binarySearch(int[] prefix, int rand){ int start = 0; int end = prefix.length; while(start < end - 1){ int mid = start + (end - start) / 2; if(prefix[mid] == rand){ return mid; }else if(prefix[mid] < rand){ start = mid; }else{ end = mid; } if (prefix[start] <= rand) { return start; } return end; }
[1, 2, 6, 7]
the probability of returning one element should be val of num / total vals
1, 2
1 1/16
2 2/16