#include <stdio.h>int array[] = { 1 , 3, 3, 1, 5, 5 , 6};int
get_only()
{int *ptmp1, *ptmp2;int *arrend = array + sizeof(array) / sizeof(int);for(ptmp1 = array; ptmp1 != arrend; ptmp1 ++){for (ptmp2 = array; ptmp2 != arrend; ptmp2++){if (ptmp2 != ptmp1 && *ptmp2 == *ptmp1){break;}}if (ptmp2 == arrend){return ptmp1 - array;}} if (ptmp1 == arrend){return -1;}
}int
main(int argc, char *argv[])
{int rst = get_only();if (rst == -1)printf("no such number\n");elseprintf("only num is : %d\n", array[rst]);return 0;
}

#include <stdio.h>int array[] = { 1 , 3, 3, 1, 5, 5 , 6 };int get_only2()
{int ret = array[0];int i;printf("len is %d\n", len);for (i = 1; i < sizeof(array) / sizeof(int); i++){printf("ret is %d\n", ret);ret = ret ^ array[i];}return ret;
}int
main(void)
{int ret = get_only2();printf("only number is %d\n", ret);return 0;
}

#include <stdio.h>void
swap(int &a, int &b)
{a = a ^ b;b = a ^ b;a = a ^ b;
}int
main(void)
{int a = 1;int b = 2;printf("before swap: a %d, b %d\n", a, b);swap(a, b);printf("after swap:  a %d, b %d\n", a, b);return 0;
}

#include <stdio.h>int
get_oxr_rst(int *arr, int len)
{int rst = 0;int idx;for(idx = 0; idx < len; idx ++){rst ^= arr[idx];} return rst;
}int
get_mask(int oxr_rst)
{int mask = 1;while((mask & oxr_rst) == 0) {mask <<= 1;} return mask;
}int
get_rst(int *arr, int len, int &A, int &B)
{if (len < 2){return 0;}int oxr_rst = get_oxr_rst(arr, len);int mask = get_mask(oxr_rst);int idx;for (idx = 0; idx < len; idx++){if (mask & arr[idx]){A ^= arr[idx];}}B = A ^ oxr_rst;return 1;
}    int
main(int argc, char *argv[])
{int arr[] = { -4, 2, 2, 4 , 3, 5, 5, 3};int A = 0, B = 0;int rst = get_rst(arr, sizeof(arr) / sizeof(int), A, B);if (rst)printf("different number is A %d and B %d\n", A, B);elseprintf("wrong args\n");return 0;
}

View Code

#include <stdio.h>struct diff_values
{int first;int second;int third;
};static int
get_oxr_rst(int *arr, int len)
{int rst = 0;int idx;for(idx = 0; idx < len; idx ++){rst ^= arr[idx];} return rst;
}//a new method to get the mask without using a loop
static int
get_first_onebit_mask(int value)
{return value & ~(value - 1);
}static int
get_mask(int *arr, int len, int oxr_rst)
{int idx;int mask = 0;/*if arr[i] = arr[j] then oxr_rst ^ arr[i] = oxr_rst ^ arr[i] thenget_first_onebit_mask(oxr_rst ^ arr[i]) = get_first_onebit_mask(oxr_rst ^ arr[j]) thenthis operation cross out all arr[i] = arr[j].then we get:mask = get_first_onebit_mask(oxr_rst ^ (arr[i])  //(arr[i] = A)^ get_first_onebit_mask(oxr_rst ^ arr[j]) //(arr[j] = B)^ get_first_onebit_mask(oxr_rst ^ arr[k]) //(stt[k] = C)then mask is what we want whose first "1" is just on postion n*/for (idx = 0; idx < len; idx++){//mask ^= get_first_onebit_mask(oxr_rst ^ arr[idx]);int tmpmask = get_first_onebit_mask(oxr_rst ^ arr[idx]);mask ^= tmpmask;}return mask;
}static int
get_rst2(int *arr, int len, struct diff_values &dv)
{if (len < 2){return 0;}int oxr_rst = get_oxr_rst(arr, len);int mask = get_first_onebit_mask(oxr_rst);int idx;int first = 0;for (idx = 0; idx < len; idx++){if (mask & arr[idx]){first ^= arr[idx];}}dv.second = first;dv.third = first ^ oxr_rst;return 1;
}int
get_rst(int *arr, int len, struct diff_values &dv)
{if (len < 3){return 0;}int oxr_rst = get_oxr_rst(arr, len);int mask = get_mask(arr, len, oxr_rst);int idx;int first = 0;for (idx = 0; idx < len; idx++){if (get_first_onebit_mask(oxr_rst ^ arr[idx]) == mask) //this operation equals to get v1.
        {first ^= arr[idx]; //this equals to the oxr operation in arr1 which contains B as the example// and the result is one of value of A, B , C.
        }}//when we get there, it means we get one of the three unique numbers;//then we get the left two numbers;//exchange first with arr[len - 1], for (idx = 0; idx < len; idx++){if (first == arr[idx]){arr[idx] = arr[idx] ^ arr[len - 1];arr[len - 1] = arr[idx] ^ arr[len - 1];arr[idx] = arr[idx] ^ arr[len - 1];break;}}dv.first = first;//only pass len - 1 values into arr, so that we can delete value firstget_rst2(arr, len - 1, dv);return 1;
}    int
main(int argc, char *argv[])
{int arr[] = { 3, 3, -4,5, 5, 8, 9 };struct diff_values dv;int rst = get_rst(arr, sizeof(arr) / sizeof(int), dv);if (rst)printf("different number is A %d , B %d , C %d\n", dv.first, dv.second, dv.third);elseprintf("wrong args\n");return 0;
}