package leetcode;
import java.util.HashMap;
import java.util.Map;
/**
* @author mercy
*Example:
*Given nums = [2, 7, 11, 15], target = 9,
*Because nums[0] + nums[1] = 2 + 7 = 9,
*return [0, 1].
*/
public class TwoSum {
public static void main(String[] args) {
int[] nums={2,0,4,9,5,7,10,9};
int target=12;
int[] arr=twoSum1(nums,target);
System.out.println(arr[0]+"--"+arr[1]);
}
public static int[] twoSum(int[] nums, int target) {
Map<Integer,Integer> map=new HashMap<>();
for(int i=0;i<nums.length;i++){
map.put(nums[i], i);
}
for(int i=0;i<nums.length;i++){
int other=target-nums[i];
if(map.containsKey(other)&&map.get(other)!=i){
return new int[] { i, map.get(other) };
}
}
throw new IllegalArgumentException("No two sum solution");
}
/**
* @param nums
* @param target
* @return
* 用Map方法
* @author mercy
*/
public static int[] twoSum1(int[] nums, int target) {
Map<Integer,Integer> map=new HashMap<>();
for(int i=0;i<nums.length;i++){
int other=target-nums[i];
if(map.containsKey(other)){
return new int[]{map.get(other),i};
}
map.put(nums[i], i);
}
throw new IllegalArgumentException("No two sum solution");
}
/**
* @param nums
* @param target
* @return
* 传统的方法
* @author mercy
*/
public static int[] twoSum2(int[] nums, int target) {
for(int i=0;i<nums.length;i++){
for(int j=i+1;j<nums.length;j++){
if(nums[j]==target-nums[i]){
return new int[] {i,j};
}
}
}
throw new IllegalArgumentException("No two sum solution");
}
}
时间: 2024-10-29 13:24:36