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	`1`	`+## 题目`
	`2`	`+`
	`3`	`+* 70. 爬楼梯`
	`4`	`+`
	`5`	`+假设你正在爬楼梯。需要 n 阶你才能到达楼顶。`
	`6`	`+`
	`7`	`+每次你可以爬 1 或 2 个台阶。你有多少种不同的方法可以爬到楼顶呢?`
	`8`	`+`
	`9`	`+注意:给定 n 是一个正整数。`
	`10`	`+`
	`11`	`+## 思路`
	`12`	`+`
	`13`	`+dp[i] = dp[i-1] + dp[i-2]`
	`14`	`+`
	`15`	`+`
	`16`	`+## 代码`
	`17`	`+`
	`18`	+```
	`19`	`+class Solution {`
	`20`	`+`
	`21`	`+ /**`
	`22`	`+ * @param Integer $n`
	`23`	`+ * @return Integer`
	`24`	`+ */`
	`25`	`+ function climbStairs($n) {`
	`26`	`+ // dp[i] = dp[i-1] + dp[i-2]`
	`27`	`+ if ($n <= 2) {`
	`28`	`+ return $n;`
	`29`	`+ }`
	`30`	`+ $dp1 = 1;`
	`31`	`+ $dp2 = 2;`
	`32`	`+ for ($i = 3; $i <= $n; $i++) {`
	`33`	`+ $temp = $dp1;`
	`34`	`+ $dp1 = $dp2;`
	`35`	`+ $dp2 = $dp2 + $temp;`
	`36`	`+ }`
	`37`	`+ return $dp2;`
	`38`	`+ }`
	`39`	`+ /**`
	`40`	`+ function climbStairs($n) {`
	`41`	`+ // dp[i] = dp[i-1] + dp[i-2]`
	`42`	`+ if ($n <= 2) {`
	`43`	`+ return $n;`
	`44`	`+ }`
	`45`	`+ $dp[1] = 1;`
	`46`	`+ $dp[2] = 2;`
	`47`	`+ for ($i = 3; $i <= $n; $i++) {`
	`48`	`+ $dp[$i] = $dp[$i-1] + $dp[$i-2];`
	`49`	`+ }`
	`50`	`+ return $dp[$n];`
	`51`	`+ }`
	`52`	`+ */`
	`53`	`+}`
	`54`	+```

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