add: 只出现一次的数字等

src/array/first-missing-positive.js

@@ -0,0 +1,58 @@
+// LeetCode 41. 缺失的第一个正数 https://leetcode-cn.com/problems/first-missing-positive/
+// LintCode 189. 丢失的第一个正整数 https://www.lintcode.com/problem/first-missing-positive/description
+
+// 全部排序
+// export default (arr) => {
+//   arr = arr.filter(item => item > 0)
+
+//   if (arr.length) {
+//     arr.sort((a, b) => a - b)
+
+//     if (arr[0] !== 1) {
+//       return 1
+//     } else {
+//       for (let n = 0, len = arr.length - 1; n < len; n++) {
+//         if (arr[n + 1] - arr[n] > 1) {
+//           return arr[n] + 1
+//         }
+//       }
+//       return arr.pop() + 1
+//     }
+//   }
+
+//   return 1
+// }
+
+// 第二解，选择排序变种
+export default (arr) => {
+  arr = arr.filter(item => item > 0)
+
+  if (arr.length) {
+    const len = arr.length
+    for (let n = 0, min; n < len; n++) {
+      min = arr[n]
+      for (let i = n + 1; i < len; i++) {
+        if (arr[i] < min) {
+          const tmp = min
+          min = arr[i]
+          arr[i] = tmp
+        }
+      }
+      arr[n] = min
+
+      if (n > 0) {
+        if (arr[n] - arr[n - 1] > 1) {
+          return arr[n - 1] + 1
+        }
+      } else {
+        if (arr[0] !== 1) {
+          return 1
+        }
+      }
+    }
+
+    return arr.pop() + 1
+  }
+
+  return 1
+}