[刷题计划]第二周第六天|二分查找

[刷题计划]第二周第六天|二分查找

文章目录

• 题目
• 题解

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题目

1351. 统计有序矩阵中的负数

剑指 Offer II 069. 山峰数组的顶部

852. 山脉数组的峰顶索引

剑指 Offer 57. 和为s的两个数字 双指针

剑指 Offer II 006. 排序数组中两个数字之和

888. 公平的糖果棒交换

1608. 特殊数组的特征值

1608. 特殊数组的特征值

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题解

1351. 统计有序矩阵中的负数

int countNegatives(int** grid, int gridSize, int* gridColSize){
    int low = 0,high = gridColSize[0],ans=  0;
    for(int i = 0;i < gridSize;i++){
        low = 0;//由于按列非递增 所以不用更新high
        while(low= 0) low = mid + 1;
            else high = mid;
        }
        ans += gridColSize[i] - high;
    }
    return ans;
}

剑指 Offer II 069. 山峰数组的顶部

int peakIndexInMountainArray(int* arr, int arrSize){
    int low = 1,high = arrSize -2,ans = 0;
    while(low <= high){
        int mid = (low + high)/2;
        if(arr[mid] > arr[mid-1]){
            ans = mid;
            low = mid + 1;
        }
        else high = mid - 1;
    }
    return ans;
}

剑指 Offer 57. 和为s的两个数字

int* twoSum(int* nums, int numsSize, int target, int* returnSize){
    int low = 0,high = numsSize - 1,*ans = malloc(sizeof(int)*2);
    *returnSize = 2;
    while(low < high){
        if(nums[low] + nums[high] > target)  high--;
        else if(nums[low] + nums[high] == target) break;
        else low++;
    }
    ans[0] = nums[low];
    ans[1] = nums[high];
    return ans;
}

剑指 Offer II 006. 排序数组中两个数字之和

int* twoSum(int* numbers, int numbersSize, int target, int* returnSize){
    int low = 0,high = numbersSize - 1,*ans = malloc(sizeof(int)*2);
    *returnSize = 2;
    while(low < high){
        if(numbers[low] + numbers[high] > target)  high--;
        else if(numbers[low] + numbers[high] == target) break;
        else low++;
    }
    ans[0] = low;
    ans[1] = high;
    return ans;
}

888. 公平的糖果棒交换

int cmp(int *a,int *b){
    return *a>*b;
}
int* fairCandySwap(int* aliceSizes, int aliceSizesSize, int* bobSizes, int bobSizesSize, int* returnSize){
    int sum1= 0,sum2 = 0,low = 0,high = 0,*ans = malloc(sizeof(int)*2);
    *returnSize = 2;
    for(int i = 0;i < aliceSizesSize;i++)    sum1 += aliceSizes[i];
    for(int i = 0;i < bobSizesSize;i++) sum2 += bobSizes[i];
    sum2 -= sum1;
    sum2/=2;
    qsort(aliceSizes,aliceSizesSize,sizeof(int),cmp);
    qsort(bobSizes,bobSizesSize,sizeof(int),cmp);
    while(low < aliceSizes && high < bobSizesSize){
        if(bobSizes[high] - aliceSizes[low] > sum2) low++;
        else if(bobSizes[high] - aliceSizes[low] == sum2)   break;
        else high++;
    }

    ans[0] = aliceSizes[low];
    ans[1] = bobSizes[high];
    return ans;
}

1608. 特殊数组的特征值

int cmp(int *a,int *b){
    return *a > *b;
}
int specialArray(int* nums, int numsSize){
    int low = 0,ans = 0;
    qsort(nums,numsSize,sizeof(int),cmp);
    while(ans<=numsSize && low < numsSize){
        while(low < numsSize&&nums[low] < ans) low++;
        if(ans == numsSize-low) return ans;
        ans++;
    }
    return -1;
}

1608. 特殊数组的特征值

int search(int* nums, int numsSize, int target){
    int low = 0,high = numsSize - 1;
    while(low <= high){
        int mid = (low + high)/2;
        if(nums[mid] == target)   return mid;
        else if(nums[mid] > target) high = mid-1;
        else                        low = mid + 1;
    }
    return -1;
}