//在两个数成对出现的数组中找到一个单独的数。比如{1,2,3。3,1,4。2},即找出4 #include <stdio.h> int find(int arr[], int len) { int i = 0; int ret = 0; for (i = 0; i < len; i++) { ret = ret^arr[i]; } return ret; } int main() { int arr1[] = { 1, 2, 2, 3, 1, 5, 3 }; int arr2[] = { 1, 2, 3,1,2,3,5,5,4,6,4 }; printf("%d ", find(arr1, sizeof(arr1) / sizeof(arr1[0]))); printf("%d ", find(arr2, sizeof(arr2) / sizeof(arr2[0]))); return 0; } <img src="http://img.blog.csdn.net/20150630154614683?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvZG91ZG91d2ExMjM0/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />