0268-missing-number.c

//计算n+1个数的和减去数组的和
int missingNumber(int* nums, int numsSize) {
    int sum = (numsSize + 1) * numsSize / 2, numsum = 0;
    for(int i = 0; i < numsSize; i++) {
        numsum += nums[i];
    }
    return sum - numsum;
}
//建立新数组查找
int missingNumber(int* nums, int numsSize) {
    int* res = (int *)calloc(numsSize + 1, sizeof(int));
    for(int i = 0; i < numsSize; i++) {
        res[nums[i]] = 1;
    }
    for(int j = 0; j < numsSize + 1; j++) {
        if(res[j] == 0) {
            return j;
        }
    }
    return -1;
}
//先排序后查找
int missingNumber(int* nums, int numsSize) {
    int i, j, min, min_index;
    for(i = 0; i < numsSize; i++) {
        min = nums[i];
        min_index = i;
        for(j = i; j < numsSize; j++) {
            if(nums[j] < min) {
                min = nums[j];
                min_index = j;
            }
        }
        j = nums[i];
        nums[i] = min;
        nums[min_index] = j;
    }
    for(i = 0; i < numsSize; i++)
        if(nums[i] != i)
            return i;
    return numsSize;
}