输入一个递增排序的数组和一个数字s，在数组中寻找两个数，使得这两个数的和为s

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题目：输入一个递增排序的数组和一个数字s，在数组中寻找两个数，使得这两个数的和为s。

注意：已经是一个递增排序数组，所以要牢牢得抓住这个特性。

#include <iostream>using namespace std;class Solution {public:  bool FindNumsWithSum(int data[], int length, int sum, int *num1, int *num2) {    if (data == NULL || length <= 1) {      return false;    }    unsigned int head = 0;    unsigned int tail = length -1;    while (head != tail) {      if (data[head]+data[tail] == sum) {        *num1 = data[head];        *num2 = data[tail];        return true;      }      else if (data[head]+data[tail] > sum) {        tail--;      }      else {        head++;      }    }    return false;  }};int main(int argc, char const *argv[]) {  int arr[6]= {1,2,4,7,12,15};  const int length = sizeof(arr)/sizeof(arr[0]);  int *num1 = new int;  int *num2 = new int;  Solution s;  bool result = s.FindNumsWithSum(arr, length, 15, num1, num2);  std::cout << result << std::endl;  std::cout << *num1 << " "<< *num2<< std::endl;  delete num1;  delete num2;  return 0;}

一段错误的代码，主要是参数传递上：

#include <iostream>using namespace std;class Solution {public:  bool FindNumsWithSum(int (&data)[6], int length, int sum, int *num1, int *num2) {    if (data == NULL || length <= 1) {      return false;    }    unsigned int head = 0;    unsigned int tail = length -1;    while (head != tail) {      if (data[head]+data[tail] == sum) {        num1 = &data[head];        num2 = &data[tail];        return true;      }      else if (data[head]+data[tail] > sum) {        tail--;      }      else {        head++;      }    }    return false;  }};int main(int argc, char const *argv[]) {  int arr[6]= {1,2,4,7,12,15};  const int length = sizeof(arr)/sizeof(arr[0]);  int *num1 = new int;  int *num2 = new int;  Solution s;  bool result = s.FindNumsWithSum(arr, length, 15, num1, num2);  std::cout << result << std::endl;  std::cout << *num1 << " "<< *num2<< std::endl;  delete num1;  delete num2;  return 0;}

此段代码会返回 0，0。
原因在于：

num1 = &data[head];num2 = &data[tail];

data为分配在栈内存的局部遍历，当FindNumsWithSum函数调用结束后，就会销毁该变量，使得num1, num2依旧保存之前的地址，具体的为：
在num1 = &data[head];之前，gdb调试结果为：

(gdb) p num1$4 = (int *) 0x602010(gdb) p num2$5 = (int *) 0x602030

在num1 = &data[head];之后，gdb调试结果为：

(gdb) p num2$6 = (int *) 0x7fffffffdd40(gdb) p data[2]$7 = 4(gdb) p &data[2]$8 = (int *) 0x7fffffffdd38

退出FindNumsWithSum之后：

(gdb) p num1$11 = (int *) 0x602010(gdb) p num2$12 = (int *) 0x602030

可见，退出FindNumsWithSum后，局部变量data销毁，num1，num2保存的地址又变回了原来的0x602010 0x602030

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