// 面試題53（三）：數組中數值和下標相等的元素 // 題目：假設一個單調遞增的數組里的每個元素都是整數并且是唯一的。請編程實 // 現一個函數找出數組中任意一個數值等于其下標的元素。例如，在數組{-3, -1, // 1, 3, 5}中，數字3和它的下標相等。//思想：因為這里也是遞增的，如果中間點的值大于下標，那后面所有值都會大于相應下標，同理中間點小于下標，前面都會小于下標 #include <iostream>int GetNumberSameAsIndex(const int* numbers, int length) {if (numbers == nullptr || length <= 0)return -1;int left = 0;int right = length - 1;while (left <= right){int middle = left + ((right - left) >> 1);if (numbers[middle] == middle)//第一種情況，中間點直接中了return middle;if (numbers[middle] > middle)//第二種情況，中間點值大于坐標，向左區間找right = middle - 1;else//第三種情況，中間點值小于坐標，向右區間找left = middle + 1;}return -1; }// ====================測試代碼==================== void Test(const char* testName, int numbers[], int length, int expected) {if (GetNumberSameAsIndex(numbers, length) == expected)printf("%s passed.\n", testName);elseprintf("%s FAILED.\n", testName); }void Test1() {int numbers[] = { -3, -1, 1, 3, 5 };int expected = 3;Test("Test1", numbers, sizeof(numbers) / sizeof(int), expected); }void Test2() {int numbers[] = { 0, 1, 3, 5, 6 };int expected = 0;Test("Test2", numbers, sizeof(numbers) / sizeof(int), expected); }void Test3() {int numbers[] = { -1, 0, 1, 2, 4 };int expected = 4;Test("Test3", numbers, sizeof(numbers) / sizeof(int), expected); }void Test4() {int numbers[] = { -1, 0, 1, 2, 5 };int expected = -1;Test("Test4", numbers, sizeof(numbers) / sizeof(int), expected); }void Test5() {int numbers[] = { 0 };int expected = 0;Test("Test5", numbers, sizeof(numbers) / sizeof(int), expected); }void Test6() {int numbers[] = { 10 };int expected = -1;Test("Test6", numbers, sizeof(numbers) / sizeof(int), expected); }void Test7() {Test("Test7", nullptr, 0, -1); }int main(int argc, char* argv[]) {Test1();Test2();Test3();Test4();Test5();Test6();Test7();system("pause");return 0; }

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轉載于:https://www.cnblogs.com/CJT-blog/p/10538096.html

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