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Author: tanfanhua

src/com/blankj/easy/_0070/Solution.java

@@ -21,5 +21,59 @@ public int climbStairs(int n) {
     public static void main(String[] args) {
         Solution solution = new Solution();
         System.out.println(solution.climbStairs(3));
+        System.out.println(solution.myClimbStairs(3));
+        System.out.println(solution.myClimbStairs2(3));
+        System.out.println(solution.myClimbStairs3(3));
+        System.out.println(solution.climbStairs(4));
+        System.out.println(solution.myClimbStairs(4));
+        System.out.println(solution.myClimbStairs2(4));
+        System.out.println(solution.myClimbStairs3(4));
+    }
+
+    public int myClimbStairs(int n) {
+        if (n <= 0) {
+            return 0;
+        }
+        if (n == 1) {
+            return 1;
+        }
+        if (n == 2) {
+            return 2;
+        }
+        return myClimbStairs(n - 1) + myClimbStairs(n - 2);
+    }
+
+    public int myClimbStairs2(int n) {
+        if (n <= 0) {
+            return 0;
+        }
+        if (n == 1) {
+            return 1;
+        }
+        if (n == 2) {
+            return 2;
+        }
+        int[] f = new int[n];
+        f[0] = 1;
+        f[1] = 2;
+        for (int i = 2; i < n; i++) {
+            f[i] = f[i - 1] + f[i - 2];
+        }
+
+        return f[n - 1];
+    }
+
+    public int myClimbStairs3(int n) {
+        if (n <= 0) {
+            return 0;
+        }
+        int f0 = 1;
+        int f1 = 1;
+        while (--n > 0) {
+            int tmp = f1;
+            f1 = f1 + f0;
+            f0 = tmp;
+        }
+        return f1;
     }
 }