Java | Leetcode Java题解之第470题用Rand7()实现Rand10()
题目：
题解：
class Solution extends SolBase {
public int rand10() {
int a, b, idx;
while (true) {
a = rand7();
b = rand7();
idx = b + (a - 1) * 7;
if (idx <= 40) {
return 1 + (idx - 1) % 10;
}
a = idx - 40;
b = rand7();
// get uniform dist from 1 - 63
idx = b + (a - 1) * 7;
if (idx <= 60) {
return 1 + (idx - 1) % 10;
}
a = idx - 60;
b = rand7();
// get uniform dist from 1 - 21
idx = b + (a - 1) * 7;
if (idx <= 20) {
return 1 + (idx - 1) % 10;
}
}
}
}