1 #include <iostream>  2 #include <cassert>  3   4 #define MAX(a, b) ((a) > (b) ? (a) : (b))  5 //判断两已排序数组是否有相同元素  6 bool sameNumber(const int* preArray, int preSize, const int* postArray, int postSize)  7  {  8     assert( preArray && postArray);  9     int preIndex = 0; 10     int postIndex = 0; 11     while (preIndex != preSize && postIndex != postSize) { 12         if (preArray[preIndex] == postArray[postIndex]) { 13             return true; 14         } 15         if (preArray[preIndex] > postArray[postIndex]) { 16             ++postIndex; 17         } else { 18             ++preIndex; 19         } 20     } 21     return false; 22 } 23  24 //求数组中最大子串 普通方法 25 int getMaxSubArrayNormal(const int* array, int size) 26 { 27     assert(array); 28     int max = array[0]; 29     for (int outIndex = 0; outIndex != size; ++outIndex) { 30         int tempValue = 0; 31         for (int inIndex = outIndex; inIndex != size; ++inIndex) { 32             tempValue += array[inIndex]; 33             if (tempValue > max) { 34                 max = tempValue; 35             } 36         } 37     } 38     return max; 39 } 40  41 //二分方法, 递归实现. 42 int getMaxSubArrayRecursion(const int* array, int size) 43 { 44     if (size == 1) { 45         return array[0]; 46     } 47     int tempSum = array[size / 2 - 1]; 48     int firstHalfMax = array[size / 2 - 1]; 49     for (int index = size / 2 - 2; index >= 0; --index) { 50         tempSum += array[index]; 51         if (tempSum > firstHalfMax) { 52             firstHalfMax = tempSum; 53         } 54     } 55     tempSum  = array[size / 2]; 56     int secondHalfMax = array[size / 2]; 57     for (int index = size / 2 + 1; index != size; ++index) { 58         tempSum += array[index]; 59         if (tempSum > secondHalfMax) { 60             secondHalfMax = tempSum; 61         } 62     } 63     return MAX(firstHalfMax + secondHalfMax,  64                MAX(getMaxSubArrayRecursion(array, size / 2),  65                    getMaxSubArrayRecursion(array + size / 2, size - size / 2))); 66 } 67  68 //动规方法, 元素如果抖为负数返回0 69 int getMaxSubArrayDP(const int* array, int size) 70 { 71     assert(array); 72     int max = 0; 73     int tempSum = 0; 74     for (int index = 0; index != size; ++index) { 75         tempSum += array[index]; 76         if (tempSum > max) { 77             max = tempSum; 78         } else if (tempSum < 0) { 79             tempSum = 0; 80         } 81     } 82     return max; 83 } 84  85 //动规, 对元素组合没有要求, 返回实际最大子串 86 int getMaxSubArrayDPGeneral(const int* array, int size) 87 { 88     assert(array); 89     int max = array[0]; 90     int tempSum = array[0]; 91     for (int index = 1; index != size; ++index) { 92         if (tempSum < 0) { 93             tempSum = array[index]; 94         } else { 95             tempSum += array[index]; 96         } 97         if (tempSum > max) { 98             max = tempSum; 99         }100     }101     return max;   102 }103 104 //同上, 不过额外返回最大子串起止下标105 int getMaxSubArrayDPGeneralWithRange(const int* array, int size, int& startIndex, int& endIndex)106 {107     assert(array);108     int max = array[0];109     int tempSum = array[0];110     startIndex = endIndex = 0;111     for (int index = 1; index != size; ++index) {112         bool updateStartIndex = false;113         if (tempSum < 0) {114             updateStartIndex = true;115             tempSum = array[index];116         } else {117             tempSum += array[index];118         }119         if (tempSum > max) {120             if (updateStartIndex) {121                 startIndex = index;122             }123             endIndex = index;124             max = tempSum;125         }126     }127     return max;   128 }129 130 int main()131 {132     int preArray[] = { 1, 3, 4, 6, 8, 9 };133     int postArray[] = { 5, 8, 10 };134     std::cout << std::boolalpha << sameNumber(preArray, 135         sizeof(preArray) / sizeof(*preArray), postArray, 136         sizeof(postArray) / sizeof(*postArray)) << std::endl;137     int maxSubArray[] = { -14, 3, 5, -6, 5, -3, -2, -1, 16, -10, -2 };138     int startIndex = 0;139     int endIndex = 0;140     std::cout << getMaxSubArrayNormal(maxSubArray, sizeof(maxSubArray) / sizeof(*maxSubArray)) << ' '141           << getMaxSubArrayDP(maxSubArray, sizeof(maxSubArray) / sizeof(*maxSubArray)) << ' '142           << getMaxSubArrayDPGeneral(maxSubArray, sizeof(maxSubArray) / sizeof(*maxSubArray)) << ' '143           << getMaxSubArrayDPGeneralWithRange(maxSubArray, sizeof(maxSubArray) / sizeof(*maxSubArray), startIndex, endIndex) << ' ' 144           << getMaxSubArrayRecursion(maxSubArray, sizeof(maxSubArray) / sizeof(*maxSubArray)) << std::endl;145     for (int index = startIndex; index <= endIndex; ++index) {146         std::cout << maxSubArray[index] << ' ' << std::flush;147     }148     std::cout << std::endl;149     return 0;150 }