3

Author: kedebug

FirstMissingPositive/FirstMissingPositive.cpp

@@ -1,62 +1,19 @@
 class Solution {
 public:
     int firstMissingPositive(int A[], int n) {
-        // Start typing your C/C++ solution below
-        // DO NOT write int main() function
-        
         int i = 0;
         while (i < n) {
-            if (A[i] != i + 1 && 0 < A[i] && A[i] <= n && A[A[i]-1] != A[i])
+            if (0 < A[i] && A[i] <= n && A[i] != A[A[i]-1]) {
                 swap(A[i], A[A[i]-1]);
-            else
-                i += 1;
+            } else {
+                i++;
+            }
         }
-        int first_positive = 0;
         for (int i = 0; i < n; i++) {
             if (A[i] != i + 1) {
-                first_positive = i + 1;
-                break;
+                return i + 1;
             }
         }
-        if (first_positive == 0)
-            first_positive = n + 1;
-        return first_positive;
+        return n + 1;
     }
 };
-
-//
-// solution 2
-//
-class Solution {
-public:
-    int firstMissingPositive(int A[], int n) {
-        // Start typing your C/C++ solution below
-        // DO NOT write int main() function
-        
-        bool find_1 = false;
-        for (int i = 0; i < n; i++) {
-            if (A[i] == 1)
-                find_1 = true;
-            else if (A[i] <= 0)
-                A[i] = 1;
-        }
-        if (!find_1) return 1;
-        for (int i = 0; i < n; i++) {
-            if (A[i] > 0 && A[i] <= n && A[A[i]-1] > 0) {
-                A[A[i]-1] = -A[A[i]-1];
-            }
-            else if (A[i] <= -1 && -A[i] <= n && A[-A[i]-1] > 0)
-                A[-A[i]-1] = -A[-A[i]-1];
-        }
-        int first_positive = 0;
-        for (int i = 0; i < n; i++) {
-            if (A[i] > 0) {
-                first_positive = i + 1;
-                break;
-            }
-        }
-        if (first_positive == 0)
-            first_positive = n + 1;
-        return first_positive;
-    }
-};