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`@@ -4,14 +4,16 @@`
`4`	`4`
`5`	`5`	`### 470.Implement Rand10() Using Rand7()`
`6`	`6`
	`7`	`+使用7个数字表达出更多个数字,构造两位7进制,(rand7() - 1) \* 7 + rand7() - 1,可以取得0-48之间的数字。如得到0-39之间的数字,使用(num % 10 + 1)等概率映射出1-10. 如得到40-48之间的数字,重新选择...直到选择到0-39之间的数字`
	`8`	`+`
`7`	`9`	```cpp
`8`	`10`	`// Some cc++`
`9`	`11`	`// transfer rand7 to rand10.`
`10`	`12`	`class Solution {`
`11`	`13`	`public:`
`12`		`- int rand10() {`
`13`		`-`
`14`		`- // [1 7] (rand7()-1) * 7 + rand7() -1 [ 0 48] >=40. descard.`
	`14`	`+ int rand10() {`
	`15`	`+// [1 7] (rand7()-1) * 7 + rand7() -1 [ 0 48] discard >=40.`
	`16`	`+// obtain [0, 39] . %10 to get 0 - 9. +1 to get [1 10]`
`15`	`17`	`int random = 49;`
`16`	`18`	`while(random>=40)`
`17`	`19`	`{`

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