33. Search in Rotated Sorted Array (#81)

Author: Kohei Asai

solutions/searchInRotatedSortedArray.test.ts

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+import search from "./searchInRotatedSortedArray";
+
+describe("33. Search in Rotated Sorted Array", () => {
+  test("#1", () => {
+    expect(search([4, 5, 6, 7, 0, 1, 2], 0)).toBe(4);
+  });
+
+  test("#2", () => {
+    expect(search([4, 5, 6, 7, 0, 1, 2], 3)).toBe(-1);
+  });
+
+  test("#3", () => {
+    expect(search([4, 5, 6, 7, 0, 1, 2], 4)).toBe(0);
+  });
+
+  test("#4", () => {
+    expect(search([3, 1], 3)).toBe(0);
+  });
+
+  test("#5", () => {
+    expect(search([7, 8, 1, 2, 3, 4, 5, 6], 2)).toBe(3);
+  });
+});

solutions/searchInRotatedSortedArray.ts

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+// 33. Search in Rotated Sorted Array
+// https://leetcode.com/problems/search-in-rotated-sorted-array/
+export default function search(nums: number[], target: number): number {
+  // check if the target value is inside a range that may be rotated
+  function isInRangeMaybeRotated(from: number, to: number) {
+    const fromValue = nums[from];
+    const toValue = nums[to];
+
+    // the range is looped when the from value is greater than the to value
+    if (fromValue > toValue) return target >= fromValue || target <= toValue;
+
+    // when the range is not looped, target must be between the from value and the to value
+    return target >= fromValue && target <= toValue;
+  }
+
+  let from = 0;
+  let to = nums.length;
+
+  while (from < to) {
+    const middle = Math.floor((from + to) / 2);
+
+    if (nums[middle] === target) return middle;
+
+    if (isInRangeMaybeRotated(from, middle - 1)) {
+      to = middle;
+    } else {
+      from = middle + 1;
+    }
+  }
+
+  return -1;
+}